SCIENCE AND SCIENTIFIC METHOD

WHAT SCIENCE IS. Science may be considered either as the product of a certain type of human activity, or as a human activity satisfactory even apart from its fruits. As an activity, it is a highly refined form of that process of reflection by which man is, in the first place, enabled to make himself at home in the world. It differs from the ordinary or common-sense process of thinking, as we shall presently see, in being more thoroughgoing, systematic, and sustained. It is common sense of a most extraordinarily refined and penetrating kind. But before examining the procedure of science, we must consider briefly its imposing product, that science whose vast structure seems to the layman so final, imposing, and irrefragable.

From the point of view of the product which is the fruit of reflective activity, Science may be defined as a body of systematized and verified knowledge, expressing in general terms the relations of exactly defined phenomena. In all the respects here noted, science may be contrasted with those matters of common knowledge, of opinion or belief which are the fruit of our casual daily thinking and experience. Science is, in the first place, a body of systematized knowledge. One has but to contrast the presentation of facts in an ordinary textbook in zooelogy with the random presentation of facts in a newspaper or in casual conversation. In science the facts bearing on a given problem are presented as completely as possible and are classified with reference to their significant bearings upon the problem. Moreover the facts gathered and the classifications of relationship made are not more or less accurate, more or less true; they are tested and verified results. That putrefaction, for example, is due to the life of micro-organisms in the rotting substance is not a mere assumption. It has been proved, tested, and verified by methods we shall have occasion presently to examine.

Scientific knowledge, moreover, is general knowledge. The relations it expresses are not true in some cases of the precise kind described, untrue in others. The relations hold true whenever these precise phenomena occur. This generality of scientific relations is closely connected with the fact that science expresses relations of exactly defined phenomena. When a scientific law expresses a certain relation between A and B, it says in effect: Given A as meaning this particular set of conditions and no others, and B as meaning this particular set of conditions and no others, then this relation holds true. The relations between exactly defined phenomena are expressed in general terms, that is, the relations expressed hold true, given certain conditions, whatever be the accompanying circumstances. It makes no difference what be the kind of objects, the law of gravitation still holds true: the attraction between objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Thus science as an activity is marked off by its method and its intent rather than by its subject-matter. As a method it is characterized by thoroughness, persistency, completeness, generality, and system. As regards its intent, it is characterized by its freedom from partiality or prejudice, and its interest in discovering what the facts are, apart from personal expectations and desires. In the scientific mood we wish to know what the nature of things is. There are men who seem to have a boundless, insatiable curiosity, who have a lifelong passion for acquiring facts and understanding the relationship between them.

SCIENCE AS EXPLANATION. The satisfactions which scientific investigators derive from their inquiries are various. There is, in the first place, the sheer pleasure of gratifying the normal human impulse of curiosity, developed in some people to an extraordinary degree. Experience to a sensitive and inquiring mind is full of challenges and provocations to look further. The appearance of dew, an eclipse of the sun, a flash of lightning, a peal of thunder, even such commonplace phenomena as the falling of objects, or the rusting of iron, the evaporation of water, the melting of snow, may provoke inquiry, may suggest the question, “Why?” Experience, as it comes to us through the senses, is broken and fragmentary. The connections between the occurrences of Nature seem casual, and connected, as it were, purely by accident. A black sky portends rain. But such an inference made by the untrained mind is merely the result of habit. A black sky has been followed by rain in the past; the same sequence of events may be expected in the future. But the connection between the two is not really understood. Sometimes experiences seem to contradict each other. The straight stick looks crooked or broken in water. The apparent anomalies and contradictions, the welter of miscellaneous facts with which we come in contact through the experiences of the senses, are clarified by the generalizations of science. The world of facts ceases to be random, miscellaneous, and incalculable. Every phenomenon that occurs is seen to be an instance of a general law that holds among all phenomena that resemble it in certain definable respects. Thus the apparent bending of the stick in water is seen to be a special case of the laws of the refraction of light; the apparent anomaly or contradiction of our sense experiences is, as we say, explained. What seemed to be a contradiction and an exception is seen to be a clear case of a regular law.

The desire for explanation in some minds is very strong. Science explains in the sense that it reduces a phenomenon to the terms of a general principle, whatever that principle may be. When we meet a phenomenon that seems to come under no general law, we are confronted with a mystery and a miracle. We do not know what to expect from it. But when we can place a phenomenon under a general law, applicable in a wide variety of instances, everything that can be said of all the other instances in which the law applies, applies also to this particular case.

Think of heat as motion, and whatever is true of motion will be true of heat; but we have had a hundred experiences of motion for everyone of heat. Think of the rays passing through this lens as bending toward the perpendicular, and you substitute for the comparatively unfamiliar lens the very familiar notion of a particular change in direction of a line, of which motion every day brings us countless examples.

It must be noticed that the explanation which science gives, is really in answer to the question, “How?” not the question, “Why?” We are said to understand phenomena when we understand the laws which govern them. But to say that certain given phenomena the appearance of dew, the falling of rain, the flash of lightning, the putrefaction of animal matter obey certain laws is purely metaphorical. Phenomena do not obey laws in the sense in which we say the child follows the commands of his parents, or the soldier those of his officer. The laws of science simply describe the relations which have repeatedly been observed to exist between phenomena. They are laws in the sense that they are invariably observed successions. When it has been found that whenever A is present, B is also present, that the presence of A is always correlated with the presence of B, and the presence of B is always correlated with the presence of A, we say we have discovered a scientific law.

Science thus explains in the sense that it reduces the multiplicity and variety of phenomena to simple and general laws. The ideal of unity and simplicity is the constant ideal toward which science moves, and its success in thus reducing the miscellaneous facts of experience has been phenomenal. The history of science in the nineteenth century offers some interesting examples. The discovery of the conservation of energy and its transformations has revealed to us the unity of force. It has shown, for example, that the phenomenon of heat could be explained by molecular motions. “Electricity annexed magnetism.” Finally the relations of electricity and light are now known; “the three realms of light, of electricity and of magnetism, previously separated, form now but one; and this annexation seems final.”

There has been thus an increasing approach toward unity, toward the summation of phenomena under one simple, general formula. Poincare, in reviewing this progress, writes:

The better one knows the properties of matter the more one sees continuity reign. Since the labors of Andrews and Van der Wals, we get an idea of how the passage is made from the liquid to the gaseous state and that this passage is not abrupt. Similarly there is no gap between the liquid and solid states, and in the proceedings of a recent congress is to be seen, alongside of a work on the rigidity of liquids, a memoir on the flow of solids....

Finally the methods of physics have invaded a new domain, that of chemistry; physical chemistry is born. It is still very young, but we already see that it will enable us to connect such phenomena as electrolysis, osmosis, and the motions of ions.

From this rapid exposition what shall we conclude?

Everything considered, we have approached unity; we have not been as quick as we had hoped fifty years ago, we have not always taken the predicted way; but, finally, we have gained ever so much ground.

The satisfaction which disinterested science gives to the investigator is thus, in the first place, one of clarification. Science, by enabling us to see the wide general laws of which all phenomena are particular instances, emancipates the imagination. It frees us from being bound by the accidental suggestions which come to us from mere personal caprice, habit, and environment, and enables us to observe facts uncolored by passions and hope, and to discover those laws of the universe which, in the words of Karl Pearson, “hold for all normally constituted minds.” In ordinary experience, our impressions and beliefs are the results of inaccurate sense observation colored by hope and fear, aversion and revulsion, and limited by accidental circumstance. Through science we are enabled to detach ourselves from the personal and the particular and to see the world, as, undistorted, it must appear to any man anywhere:

The scientific attitude of mind involves a sweeping away of all other desires in the interests of the desire to know it involves suppression of hopes and fears, loves and hates, and the whole subjective emotional life, until we become subdued to the material, able to see it frankly, without preconceptions, without bias, without any wish except to see it as it is, and without any belief that what it is must be determined by some relation, positive or negative, to what we should like it to be, or to what we can easily imagine it to be.

Besides the satisfactions of system and clarity which the sciences give, they afford man power and security. “Knowledge is power,” said Francis Bacon, meaning thereby that to know the connection between causes and effects was to be able to regulate conditions so as to be able to produce desirable effects and eliminate undesirable ones. Even the most disinterested inquiry may eventually produce practical results of a highly important character. “Science is,” as Bertrand Russell says, “to the ordinary reader of newspapers, represented by a varying selection of sensational triumphs, such as wireless telegraphy and aeroplanes, radio-activity, etc.” But these practical triumphs in the control of natural resources are often casual incidents of patiently constructed systems of knowledge which were built up without the slightest reference to their fruits in human welfare. Wireless telegraphy, for example, was made possible by the disinterested and abstract inquiry of three men, Faraday, Maxwell, and Hertz.

In alternating layers of experiment and theory these three men built up the modern theory of electromagnetism, and demonstrated the identity of light with electromagnetic waves. The system which they discovered is one of profound intellectual interest, bringing together and unifying an endless variety of apparently detached phenomena, and displaying a cumulative mental power which cannot but afford delight to every generous spirit. The mechanical details which remained to be adjusted in order to utilize their discoveries for a practical system of telegraphy demanded, no doubt, very considerable ingenuity, but had not that broad sweep and that universality which could give them intrinsic interest as an object of disinterested contemplation.

SCIENCE AND A WORLD VIEW. One of the values of disinterested science that is of considerable psychological importance is the change in attitude it brings about in man’s realization of his place in the universe. Lucretius long ago thought to free men’s minds from terror and superstition by showing them how regular, ordered, and inevitable was the nature of things. The superstitious savage walks in dread among natural phenomena. He lives in a world which he imagines to be governed by capricious and incalculable forces. To a certain extent he can, as we have seen, control these. But he is ill at ease. He is surrounded by vast ambiguous forces, and moves in a trembling ignorance of what will happen next.

To those educated to the scientific point of view, there is a solidity and assurance about the frame of things. Beneath the variability and flux, which they continually perceive, is the changeless law which they have learned to comprehend. Although they discover that the processes of Nature move on indifferent to the welfare of man, they know, nevertheless, that they are dependable and certain, that they are fixed conditions of life which, to a certain extent, can be controlled, and the incidental goods and ills of which are definitely calculable. Heraclitus, the ancient Greek philosopher, noted the eternal flux, yet perceived the steady order beneath, so that he could eventually assert that all things changed save the law of change. The magnificent regularity of natural processes has been repeatedly remarked by students of science.

THE AESTHETIC VALUE OF SCIENCE. As pointed out in the chapter on Art, scientific discovery is more than a mere tabulation of facts. It is also a work of the imagination, and gives to the worker in the scientific field precisely the same sense of satisfaction as that experienced by the creative artist. Of Kelvin his biographer writes:

Like Faraday and the other great masters in science, he was accustomed to let his thoughts become so filled with the facts on which his attention was concentrated that the relations subsisting between the various phenomena gradually dawned upon him, and he saw them, as if by some process of instinctive vision denied to others. ... His imagination was vivid; in his intense enthusiasm, he seemed to be driven rather than to drive himself. The man was lost in his subject, becoming as truly inspired as is the artist in the act of creation.

In the working-out of a principle, the systematizing of many facts under a sweeping generalization, the scientist finds a creator’s joy. He is giving form and significance to the disordered and chaotic materials of experience. The scientific imagination differs from the artistic imagination simply in that it is controlled with reference to facts. The first flash is subjected to criticism, examination, revision, and testing. But the grand generalizations of science originate in just such an unpredictable original vision. The discovery of the fitting formula which clarifies a mass of facts hitherto chaotic and contradictory is very closely akin to the process by which a poet discovers an appropriate epithet or a musician an apposite chord.

But in its products as well as in its processes, scientific investigations have a high aesthetic value. There is symmetry, order, and splendor in the relations which science reveals. The same formal beauty that appeals to us in a Greek statue or a Beethoven symphony is to be found in the universe, but on a far more magnificent scale. There is, in the first place, the sense of rhythm and regularity:

There comes [to the scientific investigator] a sense of pervading order. Probably this began at the very dawn of human reason when man first discovered the year with its magnificent object-lesson of regularly recurrent sequences, and it has been growing ever since. Doubtless the early forms that this perception of order took referred to somewhat obvious uniformities; but is there any essential difference between realizing the orderliness of moons and tides, of seasons and migrations, and discovering Bodes’s law of the relations of the planets, or Mendeleeff’s “Periodic Law” of the relations of the atomic weights of the chemical elements?

Ever since Newton’s day the harmony of the spheres has been a favorite poetic metaphor. The spaciousness of the solar system has captivated the imagination, as have the time cycles revealed by the paths of comets and meteors. The universe seems indeed, as revealed by science, to present that quality of aesthetic satisfaction which is always derived from unity in multiplicity. The stars are as innumerable as they are ordered. And it was Lucretius, the poet of naturalism, who was wakened to wonder and admiration at the ceaseless productivity, inventiveness, and fertility of Nature. We find in the revelations of science again the same examples of delicacy and fineness of structure that we admire so much in the fine arts. The brain of an ant, as Darwin said, is perhaps the most marvelous speck of matter in the universe. Again “the physicists tell us that the behaviour of hydrogen gas makes it necessary to suppose that an atom of it must have a constitution as complex as a constellation, with about eight hundred separate corpuscles."

THE DANGER OF “PURE SCIENCE.” The fascinations of disinterested inquiry are so great that they may lead to a kind of scientific intemperance. The abstracted scientific interest may become so absorbed in the working-out of small details that it becomes over-specialized, narrow, and pedantic. The pure theorist has always been regarded with suspicion by the practical man. His concern over details of flora or fauna, over the precise minutiae of ancient hieroglyphics, seems absurdly trivial in comparison with the central passions and central purposes of mankind. There are workers in every department of knowledge who become wrapt up in their specialties, forgetting the forest for the trees. There are men so absorbed in probing the crevices of their own little niche of knowledge that they forget the bearings of their researches. Especially in time of stress, of war or social unrest, men have felt a certain callousness about the interests of the abstrusely remote scholar. We shall have occasion to note presently that it is in this coldness and emancipation from the pressing demands of the moment that science has produced its most pronounced eventual benefits for mankind. But an uncontrolled passion for facts and relations may degenerate into a mere play and luxury that may have its fascination for the expert himself, but affords neither sweetness nor light to any one else. One has but to go over the lists of doctors’ dissertations published by German universities during the late nineteenth century to find examples of inquiry that seem to afford not the slightest justification in the way of eventual good to mankind.

PRACTICAL OR APPLIED SCIENCE. Thus far we have been considering science chiefly as an activity which satisfies some men as an activity in itself, by the aesthetic, emotional, and intellectual values they derive from it. But a fact at once paradoxical and significant in the history of human progress is that this most impersonal and disinterested of man’s activities has been profoundly influential in its practical fruits. The practical application of the sciences rests on the utilization of the exact formulations of pure science. Through these formulations we can control phenomena by artificially setting up relations of which science has learned the consequences, thus attaining the consequences we desire, and avoiding those we do not.

The direct influence of pure science on practical life is enormous. The observations of Newton on the relations between a falling stone and the moon, of Galvani on the convulsive movements of frogs’ legs in contact with iron and copper, of Darwin on the adaptation of woodpeckers, of tree-frogs, and of seeds to their surroundings, of Kirchhoff on certain lines which occur in the spectrum of sunlight, of other investigators on the life-history of bacteria these and kindred observations have not only revolutionized our conception of the universe, but they have revolutionized or are revolutionizing, our practical life, our means of transit, our social conduct, our treatment of disease.

Francis Bacon was one of the first to appreciate explicitly the possibilities of the control of nature in the interests of human welfare. He saw the vast possibilities which a careful and comprehensive study of the workings of nature had in the enlargement of human comfort, security, and power. In The New Atlantis he envisages an ideal commonwealth, whose unique and singular institution is a House of Solomon, a kind of Carnegie Foundation devoted to inquiry, the fruits of which might be, as they were, exploited in the interests of human happiness: “The end of our foundation is the knowledge of causes and the secret motions of things; and the enlarging of the bounds of human empire to the effecting of all things possible."

Science sometimes appears so remote and alien to the immediate concrete objects which meet and interest us in daily experience that we tend to forget that historically it was out of concrete needs and practical interests that science arose. Geometry, seemingly a clear case of abstract and theoretical science, arose out of the requirements of practical surveying and mensuration among the Egyptians. In the same way botany grew out of herb gathering and gardening.

The application of the exact knowledge gained by the pure sciences, may, if properly directed, immeasurably increase the sum of human welfare. One has but to review briefly the history of invention to appreciate this truth with vividness and detail. The great variety of the “applied sciences” shows the extent and multiplicity of the fruits of theoretical inquiry. Astronomy plays an important part in navigation; but it also earns its living by helping the surveyor and the mapmaker and by supplying the world with accurate time. Industrial chemistry offers, perhaps, the most striking examples. There is, for example, the fixation of nitrogen, which makes possible the artificial production of ammonia and potash; the whole group of dye industries made possible through the chemical production of coal tar; the industrial utilization of cellulose in the paper, twine, and leather industries; the promise of eventual production on a large scale of synthetic rubber; the electric furnace, which, with its fourteen-thousand-degree range of heat, makes possible untold increase in the effectiveness of all the chemical industries.

Industrial chemistry is only one instance. The application of theoretical inquiry in physics has made possible the telegraph, the telephone, wireless telegraphy, electric motors, and flying machines. Mineralogy and oceanography have opened up new stores of natural resources. Biological research has had diverse applications. Bacteriological inquiry has been fruitfully applied in surgery, hygiene, agriculture, and the artificial preservation of food. The principles of Mendelian inheritance have been used in the practical improvement of domestic animals and cultivated plants. The list might be indefinitely extended. The sciences arose as attempts, more or less successful, to solve man’s practical problems. They became historically cut off, as they may in the case of the pure scientist still be cut off, from practical considerations. But no matter how remote and abstract they become, they yield again practical fruits.

Applied science, if it becomes too narrowly interested in practical results, limits its own resources. Purely theoretical inquiry may be of the most immense ultimate advantage. In a sense the more abstract and remote science becomes, the more eventual promise it contains. By getting away from the confusing and irrelevant details of particular situations, science is enabled to frame generalizations applicable to a wide array of phenomena differing in detail, but having in common significant characteristics. Men can learn fruitfully to control their experience precisely because they can emancipate themselves from the immediate demands of practical life, from the suggestions that arise in the course of instinctive and habitual action. “A certain power of abstraction, of deliberate turning away from the habitual responses to a situation, was required before men could be emancipated to follow up suggestions that in the end are fruitful."

Too complete absorption in immediate problems may operate to deprive action of that sweeping and penetrating vision which a freer inquiry affords. The temporarily important may be the less important in the long run. A practical adjustment of detail may produce immediate benefits in the way of improved industrial processes and more rapid and economical production, but some seemingly obscure discovery in the most abstruse reaches of scientific theory may eventually be of untold practical significance.

Only the extremely ignorant can question the utility of, let us say, the prolonged application of the Greek intellect to the laws of conic sections. Whether we think of bridges or projectiles, of the curves of ships, or of the rules of navigation, we must think of conic sections. The rules of navigation, for instance, are in part based on astronomy. Kepler’s Laws are foundation stones of that science, but Kepler discovered that Mars moves in an ellipse round the sun in one of the foci by a deduction from conic sections.... Yet the historical fact is that these conic sections were studied as an abstract science for eighteen centuries before they came to be of their highest use.

Pasteur, whose researches are of such immediate consequence in human health, began his studies in the crystalline forms of tartrates. The tremendous commercial uses which have been made of benzene had their origin “in a single idea, advanced in a masterly treatise by Auguste Kekule in the year 1865."

Practical life has been continually enriched by theoretical inquiry. Scientific descriptions increase in value as they become absolutely impersonal, absolutely precise, and especially as they become condensed general formulas, which will be applicable to an infinite variety of particular situations. And such descriptions are necessarily abstract and theoretical.

ANALYSIS OF SCIENTIFIC PROCEDURE. Scientific method is merely common sense made more thoroughgoing and systematic. Reflection of a more or less effective kind takes place in ordinary experience wherever instinctive or habitual action is not adequate to meet a situation, whenever the individual has a problem to solve, an adjustment to make. Thinking, of some kind, goes on continually. Scientific thinking merely means careful, safeguarded, systematic thinking. It is thinking alert and critical of its own methods. As contrasted with ordinary common-sense thinking, it is distinguished by “caution, carefulness, thoroughness, definiteness, exactness, orderliness, and methodic arrangement.” We think, in any case, because we have to, being creatures born with a set of instincts not adequate to meet the conditions of our environment. We can think carelessly and ineffectively, or carefully and successfully.

Scientific method, or orderly, critical, and systematic thinking, is not applicable to one subject-matter exclusively. Examples are commonly drawn from the physical or chemical or biological laboratory, but the elements of scientific method may be illustrated in the procedure of a business man meeting a practical problem, a lawyer sifting evidence, a statesman framing a new piece of legislation. In all these cases the difference between a genuinely scientific procedure and mere casual and random common sense is the same.

Science is nothing but trained and organized common sense, differing from the latter only as a veteran may differ from a raw recruit: and its methods differ from those of common sense only so far as the guardsman’s cut and thrust differ from the manner in which a savage wields his club. The primary power is the same in each case, and perhaps the untutored savage has the more brawny arm of the two. The real advantage lies in the point and polish of the swordsman’s weapon; in the trained eye quick to spy out the weakness of the adversary; in the ready hand prompt to follow it on the instant. But, after all, the sword exercise is only the hewing and poking of the clubman refined and developed.

So, the vast results obtained by science are won by ... no mental processes, other than those which are practiced by everyone of us, in the humblest and meanest affairs of life. A detective policeman discovers a burglar from the marks made by his shoe, by a mental process identical with that by which Cuvier restored the extinct animals of Montmartre from fragments of their bones.... Nor does that process of induction and deduction by which a lady finding a stain of a peculiar kind upon her dress, concludes that somebody has upset the inkstand thereon, differ, in any way, in kind, from that by which Adams and Leverrier discovered a new planet.

The man of science, in fact, simply uses with scrupulous exactness the methods which we all, habitually and at every moment, use carelessly; and the man of business must as much avail himself of the scientific method must as truly be a man of science as the veriest bookworm of us all.

The scientific procedure becomes, as we shall see, highly complicated, involving elaborate processes of observation, classification, generalization, deduction or development of ideas, and testing. But it remains thinking just the same, and originates in some problem or perplexity, just as thinking does in ordinary life.

SCIENCE AND COMMON SENSE. It is profitable to note in some detail the ways in which scientific method, in spirit and technique, differs from common-sense thinking. It is more insistent in the first place on including the whole range of relevant data, of bringing to light all the facts that bear on a given problem. In common-sense thinking we make, as we say, snap judgments; we jump at conclusions. Anything plausible is accepted as evidence; anything heard or seen is accepted as a fact. The scientific examiner insists on examining and subjecting to scrutiny the facts at hand, on searching for further facts, and on distinguishing the facts genuinely significant in a given situation from these that happen to be glaring or conspicuous. This is merely another way of saying that both accuracy and completeness of observation are demanded, accuracy in the examination of the facts present, and completeness in the array of facts bearing on the question at hand.

Scientific thinking is thus primarily inquiring and skeptical. It queries the usual; it tries, as we say, to penetrate beneath the surface. Common sense, for example, gives suction as the explanation of water rising in a pump. But where, as at a great height above sea level, this mysterious power of suction does not operate, or when it is found that it does not raise water above thirty-two feet, common sense is at a loss. Scientific thinking tries to analyze the gross fact, and by accurately and completely observing all the facts bearing on the phenomenon endeavors to find out “what special conditions are present when the effect occurs” and absent when it does not occur. Instead of trying to fit all unusual, contradictory, or exceptional facts into a priori ideas based on miscellaneous and unsifted facts, it starts without any fixed conclusions beforehand, but carefully observes all the facts which it can secure with reference to a particular problem, deliberately seeking the exceptional and unusual as crucial instances. Thus in a sociological inquiry, the scientist, instead of accepting “common-sense” judgments (based on a variety of miscellaneous, incomplete, and unsifted facts) that certain races are inferior or superior, tries, by specific inquiries, to establish the facts of racial capacities or defects. Instead of accepting proverbial wisdom and popular estimates of the relative capacities of men and women, he tries by careful observation and experiment accurately to discover all the facts bearing on the question, and to generalize from those facts.

Scientific method thus discounts prejudice or dogmatism. A prejudice is literally a pre-judgment. Common sense sizes up the situation beforehand. Instead of examining a situation in its own terms, and arriving at a conclusion, it starts with one. The so-called hard-headed man of common sense knows beforehand. He has a definite and stereotyped reaction for every situation with which he comes in contact. These rubber-stamp responses, these unconsidered generalizations, originate in instinctive desires, or in preferences acquired through habit. Common sense finds fixed pigeon holes into which to fit all the variety of specific circumstances and conditions which characterize experience. “When its judgments happen to be correct, it is almost as much a matter of good luck as of method.... That potatoes should be planted only during the crescent moon, that near the sea people are born at high tide and die at low tide, that a comet is an omen of danger, that bad luck follows the cracking of a mirror,” all these are the results of common-sense observation. Matters of common knowledge are thus not infrequently matters of common misinformation.

Common-sense knowledge is largely a matter of uncritical belief. When there is absent scientific examination of the sources and grounds of belief, those judgments and conclusions are likely to be accepted which happen to have wide social currency and authority. In an earlier chapter, it was shown how the mere fact of an opinion prevailing among a large number of one’s group or class gives it great emotional weight. Where opinions are not determined by intelligent examination and decision, they are determined by force of habit, early education, and the social influences to which one is constantly exposed.

The scientific spirit is a spirit of emancipated inquiry as contrasted with blind acceptance of belief upon authority. The phenomenal developments of modern science began when men ceased to accept authoritatively their beliefs about man and nature, and undertook to examine phenomena in their own terms. The phenomenal rise of modern science is coincident with the collapse of unquestioning faith as the leading ingredient of intellectual life.

Common sense renders men peculiarly insensitive to the possibilities of the novel, peculiarly susceptible to the influence of tradition. It was common sense that credited the influence of the position of the stars upon men’s welfare, the power of old women as witches, and the unhealthiness of night air. It was common sense also that ridiculed Fulton’s steamboat, laughed at the early attempts of telegraphy and telephony, and dismissed the aeroplane as an interesting toy. The characteristic feature of common sense or empirical thinking is its excess traditionalism, its wholesale acceptance of authority, its reliance upon precedent. Where beliefs are not subjected to critical revision and examination, to the constant surveillance of the inquiring intelligence, there will be no criterion by which to estimate the true and the false, the important and the trivial. All beliefs that have wide social sanction, or that chime in with immediate sense impressions, established individual habits, or social customs will be accepted with the same indiscriminate hospitality. To common sense the sun does appear to go round the earth; the stick does appear broken in water. Thus “totally false opinions may appear to the holder of them to possess all the character of rationally verifiable truth.”

The dangers and falsities of common-sense judgments are conditioned not only by expectations and standards fixed by the social environment, but by one’s own personal predilections and aversions. Recent developments in psychology have made much of the fact that many of our so-called reasoned judgments are rationalizations, secondary reasons found after our initial, primary, and deep-seated emotional responses have been made. They are the result of emotional “complexes,” fears, expectations, and desires of which we are not ourselves conscious. It is from these limiting conditions of personal preference and social environment that scientific method frees us.

“The two mechanisms which manifest themselves in our example of the politician, the unconscious origin of beliefs and actions, and the subsequent process of rationalization to which they are subjected, are of fundamental importance in psychology.” (Bernard Hart: The Psychology of Insanity, pp. 64-66.)]

Again, even where common-sense judgments are not particularly qualified by such conditions, they are frequently based upon the observation of purely accidental conjunctions of circumstances. A sequence once or twice observed is taken as the basis of a causal relation. This gives rise to what is known in technical logic as the post hoc ergo propter hoc fallacy; that is, the assumption that because one thing happens after another, therefore it happens because of it. Many superstitions probably had their origin in such chance observations, and belief in them is strengthened by some accidental confirmation. Thus if a man walks under a ladder one day and dies the next, the believer in the superstition that walking under a ladder brings fatal results will find in this instance a clear ratification of his belief. There seems to be an inveterate human tendency to seek for causes, and by those who are not scientific inquirers causes are lightly assigned. It is easiest and most plausible to assign as a cause an immediately preceding circumstance. Exceptional or contradictory circumstances are then either unnoticed or pared down to fit the belief.

Scientific method does not depend on such chance conjunctions of circumstance, but controls its observations or experimentally arranges conditions so as to discover what are the conditions necessary to produce given effects, or what effects invariably follow from given causes. It does not accept a chance conjunction as evidence of an invariable relation, but seeks, under regulated conditions, to discover what the genuinely invariable relations are. This method of controlling our generalizations about the facts of experience, we shall presently examine in some detail.

CURIOSITY AND SCIENTIFIC INQUIRY. Curiosity, the instinctive basis of the desire to know, is the basis of scientific inquiry. Without this fundamental desire, there could be no sustaining motive to deep and thoroughgoing scientific research, for theoretical investigations do not always give promise of immediate practical benefits. The scientific interest is a development of that restless curiosity for a knowledge of the world in which they are living which children so markedly exhibit. Beginning as a kind of miscellaneous and omnivorous appetite for facts of whatever description, it grows into a desire to understand the unsuspected and hidden relations between facts, to penetrate to the unities discoverable beneath the mysteries and multiplicities of things.

The scientific mood is thus in the first place a sheer instinctive curiosity, a basic passion for facts. It is this which sustains the scientific worker in the sometimes long and dreary business of collecting specimens, instances, details. Many of the most notable scientific advances, as Lord Kelvin pointed out, must be attributed to the most protracted and unmitigated drudgery in the collection of facts, a thoroughgoing and trying labor in which the scientific worker could persist only when fortified by an eager and insistent curiosity. This “hodman’s work” is the basis of the great generalizations which constitute the framework of the modern scientific systems. “The monotonous and quantitative work of star-cataloguing has been continued from Hipparchus, who began his work more than a century before Christ, work which is continued even to the present day. This work, uninspiring as it seems, is yet an essential basis for the applications of astronomy, the determination of time, navigation, surveying. Furthermore, without good star places, we can have no theory of the motions of the solar system, and without accurate catalogues of the stars we can know nothing of the grander problems of the universe, the motion of our sun among the stars, or of the stars among themselves."

Not only is curiosity a sustaining motive in the drudgery of collection and research incident and essential to scientific generalization; it alone makes possible that suspense of judgment which is necessary to fruitful scientific inquiry. This suspense is, as we have already seen, difficult for most men. Action demands immediate decision, and inquiry deliberately postpones decision. It is only a persistent desire to “get at the bottom of the matter” that will act as a check upon the demands of social life and of individual impatience which rush us to conclusions. In most men, as earlier noted, the sharp edge of curiosity becomes easily blunted. They are content, outside their own immediate personal interests, “to take things for granted.” They glide over the surfaces of events, they cease to query the authenticity of facts, or to examine their relevance and their significance, or to be concerned about their completeness. For an example, one has but to listen to or partake in the average discussion of any political or social issue of the present day. There are few men who retain, even as far as middle life, a genuinely inquiring interest in men and affairs. Their curiosity is dulled by fatigue and the pressure of their own interests and preoccupations, and they allow their prejudices and formulas to pass for judgments and conclusions. The scientist is the man in whom curiosity has become a permanent passion, who, as long as he lives, is unwilling to forego inquiry into the processes of Nature, or of human relations.

THINKING BEGINS WITH A PROBLEM. While the general habit of inquiry is developed in the satisfaction of the instinct of curiosity, any particular investigation begins with a felt difficulty. By difficulty is not meant one of an imperative and practical kind, but any problem whether theoretical or practical. For many men, it is true, thinking occurs only when instinct and habit are inadequate to adjust them to their environment. Any problem of daily life affords an example. To borrow an illustration from Professor Dewey:

A man traveling in an unfamiliar region comes to a branching of the roads. Having no sure knowledge to fall back upon, he is brought to a standstill of hesitation and suspense. Which road is right? And how shall the perplexity be resolved? There are but two alternatives. He must either blindly and arbitrarily take his course, trusting to luck for the outcome, or he must discover grounds for the conclusion that a given road is right.

To the inquiring mind, purely theoretical difficulties or discrepancies will provoke thought. To the astronomer an unaccounted-for perturbation in the path of a planet provokes inquiry; the chemist is challenged by a curious unexplained reaction of two chemical elements, the biologist, anterior to the discovery of micro-organisms, by the putrefaction of animal tissues. The degree to which curiosity persists and the extent of training a man has had in a given field largely determine the kind of situations that will provoke inquiry. “A primrose by the river’s brim” may be simply a primrose to one man, while to another, a botanist, it may suggest an interesting and complex problem of classification.

But however remote and recondite thinking becomes, however far removed from immediate practical concerns, it occurs essentially in a situation analogous to the “forked-road situation” described above. The situation as it stands is confused, ambiguous, uncertain. In a practical problem, for example, there are two or more courses of action open to us, all of them giving promise as solutions of our difficulties. We aim through reflection to reduce the uncertainty, to clarify the situation, to discover more clearly the consequences of the various alternatives which suggest themselves to us. When action is unimpeded, suggestions flow on just as they arise in our minds. This is illustrated best in the reveries of a day-dream when casual and disconnected fancies follow each other in random and uncontrolled succession. But when there is a problem to be settled, an ambiguity to be resolved, suggestions are held in check and controlled with reference to the end we have in view; each suggestion is estimated with regard to its relevance to the problem in hand. Every idea that arises is, so to speak, queried: “Is it or is it not a solution to our present difficulty?”

We are indebted to Professor Dewey, for an analysis of the thought process. Every instance of thinking reveals five steps:

(1) A felt difficulty, (2) its location and definition, (3) suggestions of possible solutions, (4) development by reasoning of the bearings of the most promising suggestion, (5) further observation or experiment leading to its acceptance or rejection, that is a conclusion either of belief or disbelief.

When instinct or habit suffices to adjust us to our environment, action runs along smoothly, freely, uninterruptedly. In consequence the provocation to thinking may at first be a mere vague shock or disturbance. We are, as it were, in trouble without knowing precisely what the trouble is. We must carefully inquire into the nature of the problem before undertaking a solution. To take a simple instance, an automobile may suddenly stop. We know there is a difficulty, but whether it is a difficulty with the transmission, with the carburetor, or with the supply of gasoline, we cannot at first tell. Before we do anything else in solving our problem, we find out literally and precisely what the trouble is. To take a different situation, a doctor does not undertake to prescribe for a patient until he has diagnosed the difficulty, found out precisely what the features of the problem are.

The second step after the situation has been examined and its precise elements defined, is suggestion. That is, we consider the various possibilities which suggest themselves as solutions to our problem. There may be several ways of temporarily repairing our engine; the doctor may think of two or three possible treatments for a disease. In one sense, suggestion is uncontrollable. The kind of suggestions that occur to an individual depend on his “genius or temperament,” on his past experiences, on his hopes or fears or expectations when that particular situation occurs. We can, however, through the methods of science, control suggestions indirectly. We can do this, in the first place, by reexamining the facts which give rise to suggestion. If upon close examination, the facts appear differently from what they did at first, we will derive different inferences from them. Different suggestions will arise from the facts A, B, C, than from the facts A’, B’, C’. Again we can regulate the conditions under which credence is given to the various suggestions that arise. These suggestions are entertained merely as tentative, and are not accepted until experimentally verified. “The suggested conclusion as only tentatively entertained constitutes an idea.”

After the variety of suggestions that proffer themselves as solutions to a problem have been considered, the third step is the logical development of the idea or suggestion that gives most promise of solving the difficulty. That is, even before further facts are sought, the idea that gives promise of being a solution is followed out to its logical consequences. Thus, for example, astronomers were for a long time puzzled by unexplained perturbations in the path of the planet Uranus. The suggestion occurred that an unseen planet was deflecting it from the path it should, from observation and calculation, be following. If this were the case, from the amount of deflection it was mathematically calculated, prior to any further observation, that the supposed planet should appear at a certain point in space. It was by this deductive elaboration that the planet Neptune was discovered. It was figured out deductively that a planet deflecting the path of the planet Uranus by just so-and-so much should be found at just such and such a particular point in the heavens. When the telescopes were turned in that direction, the planet Neptune was discovered at precisely the point deductively forecast.

The elaboration of an idea through reasoning it out may sometimes lead to its rejection. But in thinking out its details we may for the first time note its appositeness to the solution of the problem in hand. The gross suggestion may seem wild and absurd, but when its bearings and consequences are logically developed there may be some item in the development which dovetails into the problem as its solution. William James gives as the outstanding feature of reasoning, “sagacity, or the perception of the essence." By this he meant the ability to single out of a complex situation or idea the significant or key feature. It is only by a logical development of a suggested solution to a problem that it is possible to hit upon the essence of the matter for a particular situation, to single out of a gross total situation, the key to the phenomenon. “In reasoning, A may suggest B; but B, instead of being an idea which is simply obeyed by us, is an idea which suggests the distinct additional idea C. And where the train of suggestion is one of reasoning distinctively so-called as contrasted with mere ‘revery,’ ... the ideas bear certain inward relations to each other which we must carefully examine. The result C yielded by a true act of reasoning is apt to be a thing voluntarily sought, such as the means to a proposed end, the ground for an observed effect, or the effect of an assumed cause." Thus what at first sight might seem a fantastic suggestion may, when its bearings are logically followed out, be seen in one of its aspects to be the key to the solution of a problem. To primitive man it might have seemed absurd to suggest that flowing water might be used as power; to the man in Franklin’s day that the same force that was exhibited in the lightning might be used in transportation and in lighting houses.

But no thinking is conclusive until after the experimental certification and warranting of the idea which has been held in mind as the solution of the problem. By deduction, by logical elaboration of an idea, we find its adoption involves certain consequences. Some of the logical consequences which follow from an idea may indicate that it is a plausible solution of our problem. But no matter how plausible a suggestion looks, until it is verified by observation or experiment the thinking process is not concluded, is not finished, as we say, conclusively. When an idea or a suggestion has been developed, and seen to involve as an idea certain inevitable logical consequences, the idea must be tested by further observation and experiment. Suggestions arise from facts and must be tested by them. Until the suggestion is verified, it remains merely a suggestion, a theory, a hypothesis, an idea. It is only when the consequences implied logically in the very idea itself are found in the actual situation that the idea is accepted as a solution to the problem. Sometimes the suggestion may be verified by observation; sometimes conditions must be deliberately arranged for testing its adequacy. In either case it is only when the facts of the situation correspond to the conditions theoretically involved that the tentative idea is accepted as a conclusion.

Thus a treatment that is regarded by the doctor as a possible cure can be called an actual cure only when its beneficent results are observed. The supposition about the planet Neptune is only verified when the planet is actually observed in the heavens. Thinking ends, as it begins, in observation. At the beginning the facts are carefully examined to see precisely where the difficulty lies; at the end they are again examined to see whether an idea, an entertained hypothesis, a suggested solution, can be verified in actual observable results.

THE QUALITY OF THINKING SUGGESTION. The quality of thinking varies, first, with the fertility of suggestion of the analyzing mind. Ease of suggestion, in the first place, depends on innate individual differences. There are some minds so constituted that every fact provokes a multitude of suggestions. Readiness in responding with “ideas” to any experience is dependent primarily on initial differences in resilience and responsiveness. But differences in training and past experience are also contributory. A man who has much experience in a given field, say in automobile repairing, will, given a difficulty, not only think of more suggestions, but think more rapidly in that field.

Again persons differ in range or number of suggestions that occur. The quality of the thinking process and of the results it produces depends, in part, on the variety of suggestions which occur to an individual in the solution of a given problem. If too few suggestions occur one may fail to hit upon any promising solution. If too many suggestions occur one may be too confused to arrive at any conclusion at all. Whether an individual has few or many suggestions depends largely on native differences. It depends, also, however in part, on acquaintance with a given field. And the fertility of suggestions may be increased by a careful survey and re-survey of the facts at hand, and by the deliberate searching-out of further facts from which further suggestions may be derived. Suggestions differ, finally, in regard to depth or significance; by nature and by training, individuals produce ideas of varying degrees of significance in the solution of problems. Ease and versatility of suggestion not infrequently connote superficiality; to make profound and far-reaching suggestions takes time.

It is further requisite, as already pointed out, that the analyzing mind be free from prejudice. Thinking is continually qualified, as we have seen, by preferences and aversions. Every prejudice, every a priori belief we have, literally prejudges the inquiry. Whenever we are moved by a “predominant passion,” we cannot survey the facts impartially. It is hard to think clearly and justly about people whom we love or hate, or to estimate with precision the morality of actions toward which we are moved by very strong impulses. It is only the mind that remains resolutely emancipated from the compulsions of habit and circumstances, that persists in surveying facts as they are, letting the chips, so to speak, fall where they will, that can be really effective in thinking. In the physical sciences it is comparatively easy to start with no prejudices; in social inquiries where we are bound by traditions, loyalties, and antipathies it is much more difficult.

Not the least essential to effective thinking is persistence and thoroughness of investigation. Since we are primarily creatures of action, we crave definiteness and immediacy of decision, and there is a constant temptation to rush to a conclusion. In order to attain genuine completeness of the facts and certainty and accuracy as to what the facts are, long, unwavering persistence is required. There must be persistence, moreover, not merely because of the length of time and the amount of labor involved in the collection of data; steadiness is required in holding in mind the end or purpose of the investigation. Too often in inquiry into the facts of human relations, the specific problem is forgotten and facts are collected with an indiscriminate omnivorousness. There is in such cases plodding, but of an unenlightened and fruitless sort. Not only persistency but consistency is required. The investigation must be steadily carried on with persistent and unwavering reference to the specific business in hand.

Effective thinking depends further on familiarity with the field of facts under investigation. Even the most ready and fertile of minds, the most orderly habits of thought, are at a loss without a store of material; that is, facts from which suggestions may arise. And this store of materials can only be attained through a thoroughgoing acquaintance with the particular field of inquiry. Thinking aims to explain the relations between facts, and an intimate acquaintance with facts involved in a given situation is prerequisite to any generalization whatsoever.

While the native fertility of given minds cannot be controlled, suggestions can be controlled indirectly. Suggestions arise from the data at hand, but the data themselves change under more precise conditions of observation, and the suggestions that arise from them change in consequence. The whole elaborate apparatus of science, its instruments of precision, are designed to yield an exact determination of the precise nature of the data at hand. The scientist attempts to prevent “reading-in” of meanings. “Reading-in” of meanings may be due to various causes. In the first place there may be purely physical causes: a dim light, a fog, a cracked window-pane are examples of how ordinary observation may lead us astray. Again, physiological causes may be at work to distort sensations: imperfection’s in the sense organs, fatigue, illness, and the like are examples. But not least among the causes of error must be set psychological causes. That is, we read facts differently in the light of what we fear or hope, like or dislike, expect or recall. We see things the way we want them to be, or the way previous experience has taught us to expect them to be.

Both physiological and psychological causes may be checked up by instruments. Indeed, one of the chief utilities of instruments of precision is that they do serve to check up personal error. They prevent scientific inquirers from reading in meanings to which they are led by hope, fear, preference, or aversion. They help us to see the facts as they are, not as for various social and personal reasons we want or expect them to be. They help to give precise and permanent impressions which are not dependent for their discovery or for their preservation on the precariousness of human observation or memory.

CLASSIFICATION. Next only in importance to accurate observation of the facts is their classification. Objects of experience as they come to us through the senses appear in a sequence which is random and chaotic. But in order to deal effectively with our experience we must arrange facts according to their likenesses and differences. Whenever we discover certain striking similarities between facts, we classify them, place them in a class, knowing that what will apply to one will apply to all. Some logicians go so far as to say that science cannot go any further than accurate classification. In the words of Poincare:

The most interesting facts are those which may serve many times; these are the facts which have a chance of coming up again. We have been so fortunate as to have been born in a world where there are such. Suppose that instead of sixty chemical elements there were sixty milliards of them, that they were not some common, the others rare, but that they were equally distributed. Then, every time we picked up a new pebble there would be great probability of its being formed of some unknown substance; all that we knew of other pebbles would be worthless for it; before each new object we should be as the new-born babe; like it we could only obey our caprices or our needs. Biologists would be just as much at a loss if there were only individuals and no species, and if heredity did not make sons like their fathers.

The aim of classification in science is grouping in such a way as to make manifest at once similarities in the behavior of objects. That characteristic is selected as a basis of classification with which is correlated the greatest number of other characteristics belonging to the facts in question. It would be possible to classify all living things according to color, but such a classification would be destitute of scientific value. Biology offers some interesting examples of how an illuminating classification may be made on the basis of a single characteristic. It has been found, for example, that the differences or resemblances of animals are correlated with corresponding differences or resemblances in their teeth. In general, the function of classification may be summarized in Huxley’s definition as modified by Jevons:

By the classification of any series of objects is meant the actual or ideal arrangement together of those things which are like and the separation of those things which are unlike, the purpose of the arrangement being, primarily, to disclose the correlations or laws of union of properties and circumstances, and, secondarily, to facilitate the operations of the mind in clearly conceiving and retaining in memory the characters of the object in question.

It should be noted that the object of classification is not simply to indicate similarities but to indicate distinctions or differences. In scientific inquiry, differences are as crucial in the forming of generalizations as similarities. It is only possible to classify a given fact under a scientific generalization when the given fact is set off from other facts, when it is seen to be the result of certain special conditions.

If a man infers from a single sample of grain as to the grade of wheat of the car as a whole, it is induction, and under certain circumstances, a sound induction; other cases are resorted to simply for the sake of rendering that induction more guarded and correct. In the case of the various samples of grain, it is the fact that the samples are unlike, at least in the part of the carload from which they are taken, that is important. Were it not for this unlikeness, their likeness in quality would be of no avail in assisting inference.

EXPERIMENTAL VARIATION OF CONDITIONS. In forming our generalizations from the observation of situations as they occur in Nature, we are at a disadvantage. If we observe cases just as we find them, there is much present that is irrelevant to our problem; much that is of genuine importance in its solution is hidden or obscure. In experimental investigation we are, in the words of Sir John Herschel, “active observers”; we deliberately invent crucial or test cases. That is, we deliberately arrange conditions so that every factor is definitely known and recognized. We then introduce into this set of completely known conditions one change, one new circumstance, and observe its effect. In Mill’s phrase, we “take a phenomenon home with us,” and watch its behavior. Mill states clearly the outstanding advantage of experimentation over observation:

When we can produce a phenomenon artificially, we can take it, as it were, home with us, and observe it in the midst of circumstances with which in all other respects we are accurately acquainted. If we desire to know what are the effects of the cause A, and are able to produce A by means at our disposal, we can generally determine at our own discretion ... the whole of the circumstances which shall be present along with it; and thus, knowing exactly the simultaneous state of everything else which is within the reach of A’s influence, we have only to observe what alteration is made in that state by the presence of A.

For example, by the electric machine we can produce, in the midst of known circumstances, the phenomena which Nature exhibits on a grander scale in the form of lightning and thunder. Now let any one consider what amount of knowledge of the effects and laws of electric agency mankind could have obtained from the mere observation of thunderstorms, and compare it with that which they have gained, and may expect to gain, from electrical and galvanic experiments....

When we have succeeded in isolating the phenomenon which is the subject of inquiry, by placing it among known circumstances, we may produce further variations of circumstances to any extent, and of such kinds as we think best calculated to bring the laws of the phenomenon into a clear light. By introducing one well-defined circumstance after another into the experiment, we obtain assurance of the manner in which the phenomenon behaves under an indefinite variety of possible circumstances. Thus, chemists, after having obtained some newly discovered substance in a pure state, ... introduce various other substances, one by one, to ascertain whether it will combine with them, or decompose them, and with what result; and also apply heat or electricity or pressure, to discover what will happen to the substance under each of these circumstances.

Through experiment, we are thus enabled to observe the relation of specific elements in a situation. We are, furthermore, enabled to observe phenomena which are so rare in occurrence that it is impossible to form generalizations from them or improbable that we should even notice them: “We might have to wait years or centuries to meet accidentally with facts which we can readily produce at any moment in a laboratory; and it is probable that many of the chemical substances now known, and many excessively useful products, would never have been discovered at all, by waiting till Nature presented them spontaneously to our observation.” And phenomena, such as that of electricity, which can only be understood when the conditions of their occurrence are varied, are presented to us in Nature most frequently in a fixed and invariable form.

GENERALIZATIONS, THEIR ELABORATION AND TESTING. So far we have been concerned with the steps in the control of suggestion, the reexamination of the facts so that significant suggestions may be derived, and the elimination of the significant from the insignificant in the elements of the situation as it first confronts us. In logically elaborating a suggestion, as we have already seen, we trace out the bearings of a given situation. We expand it; we see what it implies, what it means. Thus, if we came, for example, to a meeting that had been scheduled, and found no one present, we might have several solutions arise in our minds. The meeting, we might suppose, had been transferred to another room. If that were the case, there would probably be some notice posted. In all cases of deductive elaboration, we go through what might be called the If-Then process. If such-and-such is the case, then such-and-such will follow. We can then verify our suggested solution to a problem, by going back to the facts, to see whether they correspond with the implications of our suggestion. We may, to take another example, think that a man who enters our office is an insurance agent, or a book solicitor who had said he would call upon us at a definite date. If such is the case, he will say such-and-such things. If he does say them, then our suggestion is seen to be correct. The advantages of developing a suggestion include the fact that some link in the logical chain may bear a more obvious relation to our problem than did the undeveloped suggestion itself.

The systematic sciences consist of such sets of principles so related that any single term implies certain others, which imply certain others and so on ad infinitum.

After the facts have been elaborated, the generalization, however plausible it may seem, must be subjected to experimental corroboration. That is, if a suggestion is found through local elaboration to mean A, B, C, then the situation must be reexamined to see if the facts to be found tally with the facts deduced. In the case cited, the suggestion that the man who entered the room was the insurance agent we expected would be verified if he immediately broached the subject and the fact, say, of a previous conversation. In the case of disease, if the illness is typhoid, we shall find certain specific conditions in the patient. If these are found, the suggestion of typhoid is verified.

The reliability of generalizations made by this scientific procedure varies according to several factors. It varies, in the first place, according to the correspondence of the predictions made on the basis of the generalization, with subsequent events. The reason we say the law of gravitation holds true is because in every instance where observations or experiments have been made, the results have tallied precisely with expectations based upon the generalization. We can, to a certain extent, determine the reliability of a generalization before comparing our predictions with subsequent events. If a generalization made contradicts laws that have been established in so many instances that they are practically beyond peradventure, it is suspect. A law, for example, that should be an exception to the laws of motion or gravitation, is a priori dubious.

If an induction conflicts with stronger inductions, or with conclusions capable of being correctly deduced from them, then, unless on reconsideration it should appear that some of the stronger inductions have been expressed with greater universality than their evidence warrants, the weaker one must give way. The opinion so long prevalent that a comet, or any other unusual appearance in the heavenly regions, was the precursor of calamities to mankind, or to those at least who witnessed it; the belief in the veracity of the oracles of Delphi or Dodona; the reliance on astrology, or on the weather prophecies in almanacs, were doubtless inductions supposed to be grounded on experience.... What has really put an end to these insufficient inductions is their inconsistency with the stronger inductions subsequently obtained by scientific inquiry, respecting the causes on which terrestrial events really depend.

THE QUANTITATIVE BASIS OF SCIENTIFIC PROCEDURE. Science is science, some scientists insist, in so far as it is mathematical. That is, in the precise determination of facts, and in their repetition with a view to their exact determination, quantities must be known. The sciences have developed in exactness, in so far as they have succeeded in expressing their formulations in numerical terms. The physical sciences, such as physics and chemistry, which have been able to frame their generalizations from precise quantities, have been immeasurably more certain and secure than such sciences as psychology and sociology, where the measurement of exact quantities is more difficult and rare. Jevons writes in his Principles of Science:

As physical science advances, it becomes more and more accurately quantitative. Questions of simple logical fact resolve themselves after a while into questions of degree, time, distance, or weight. Forces hardly suspected to exist by one generation are clearly recognized by the next, and precisely measured by the third generation.

The history of science exhibits a constant progress from rude guesses to precise measurement of quantities. In the earliest history of astronomy there were attempts at quantitative determinations, very crude, of course, in comparison with the exactness of present-day scientific methods.

Every branch of knowledge commences with quantitative notions of a very rude character. After we have far progressed, it is often amusing to look back into the infancy of the science, and contrast present with past methods. At Greenwich Observatory in the present day, the hundredth part of a second is not thought an inconsiderable portion of time. The ancient Chaldreans recorded an eclipse to the nearest hour, and the early Alexandrian astronomers thought it superfluous to distinguish between the edge and center of the sun. By the introduction of the astrolabe, Ptolemy, and the later Alexandrian astronomers could determine the places of the heavenly bodies within about ten minutes of arc. Little progress then ensued for thirteen centuries, until Tycho Brahe made the first great step toward accuracy, not only by employing better instruments, but even more by ceasing to regard an instrument as correct.... He also took notice of the effects of atmospheric refraction, and succeeded in attaining an accuracy often sixty times as great as that of Ptolemy. Yet Tycho and Hevelius often erred several minutes in the determination of a star’s place, and it was a great achievement of Roemer and Flamsteed to reduce this error to seconds. Bradley, the modern Hipparchus, carried on the improvement, his errors in right ascension, according to Bessel, being under one second of time, and those of declination under four seconds of arc. In the present day the average error of a single observation is probably reduced to the half or the quarter of what it was in Bradley’s time; and further extreme accuracy is attained by the multiplication of observations, and their skillful combination according to the theory of error. Some of the more important constants... have been determined within a tenth part of a second of space.

The precise measurement of quantities is important because we can, in the first place, only through quantitative determinations be sure we have made accurate observations, observations uncolored by personal idiosyncrasies. Both errors of observation and errors of judgment are checked up and averted by exact quantitative measurements. The relations of phenomena, moreover, are so complex that specific causes and effects can only be understood when they are given precise quantitative determination. In investigating the solubility of salts, for example, we find variability depending on differences in temperature, pressure, the presence of other salts already dissolved, and the like. The solubility of salt in water differs again from its solubility in alcohol, ether, carbon, bisulphide. Generalization about the solubility of salt, therefore, depends on the exact measurement of the phenomenon under all these conditions.

The importance of exact measurement in scientific discovery and generalization may be illustrated briefly from one instance in the history of chemistry. The discovery of the chemical element argon came about through some exact measurements by Lord Rayleigh and Sir William Ramsay of the nitrogen and the oxygen in a glass flask. It was found that the nitrogen derived from air was not altogether pure; that is, there were very minute differences in the weighings of nitrogen made from certain of its compounds and the weight obtained by removing oxygen, water, traces of carbonic acid, and other impurities from the atmospheric air. It was found that the very slightly heavier weight in one case was caused by the presence of argon (about one and one third times as heavy as nitrogen) and some other elementary gases. The discovery was here clearly due to the accurate measurement which made possible the discovery of this minute discrepancy.

It must be noted in general that accuracy in measurement is immediately dependent on the instruments of precision available. It has frequently been pointed out that the Greeks, although incomparably fresh, fertile, and direct in their thinking, yet made such a comparatively slender contribution to scientific knowledge precisely because they had no instruments for exact measurement. The thermometer made possible the science of heat. The use of the balance has been in large part responsible for advances in chemistry.

The degree to which sciences have attained quantitative accuracy varies among the physical sciences. The phenomena of light are not yet subject to accurate measurement; many natural phenomena have not yet been made the subject of measurement at all. Such are the intensity of sound, the phenomena of taste and smell, the magnitude of atoms, the temperature of the electric spark or of the sun’s atmosphere.

The sciences tend, in general, to become more and more quantitative. All phenomena “exist in space and involve molecular movements, measurable in velocity and extent.” The ideal of all sciences is thus to reduce all phenomena to measurements of mass and motion. This ideal is obviously far from being attained. Especially in the social sciences are quantitative measurements difficult, and in these sciences we must remain therefore at best in the region of shrewd guesses or fairly reliable probability.

STATISTICS AND PROBABILITY. While in the social sciences, exact quantitative measurements are difficult, they are to an extent possible, and to the extent that they are possible we can arrive at fairly accurate generalizations as to the probable occurrence of phenomena. There are many phenomena where the elements are so complex that they cannot be analyzed and invariable causal relations established.

In a study of the phenomena of the weather, for example, the phenomena are so exceedingly complex that anything approaching a complete statement of their elements is quite out of the question. The fallibility of most popular generalizations in these fields is evidence of the difficulty of dealing with such facts. Must we be content then simply to guess at such phenomena? ... In instances of this sort, another method ... becomes important: The Method of Statistics. In statistics we have an exact enumeration of cases. If a small number of cases does not enable us to detect the causal relations of a phenomenon, it sometimes happens that a large number, accurately counted, and taken from a field widely extended in time and space, will lead to a solution of the problem.

If we find, in a wide variety of instances, two phenomena occurring in a certain constant correlation, we infer a causal relation. If the variations in the frequency of one correspond to variations in the frequency of the other, there is probability of more than connection by coincidence.

The correlation between phenomena may be measured mathematically; it is possible to express in figures the exact relations between the occurrence of one phenomenon and the occurrence of another. The number which expresses this relation is called the coefficient of correlation. This coefficient expresses relationship in terms of the mean values of the two series of phenomena by measuring the amount each individual phenomenon varies from its respective mean. Suppose, for example, that in correlating crime and unemployment, the coefficient of correlation were found to be .47. If in every case of unemployment crime were found and in every case of crime, unemployment, the coefficient of correlation would be +1. If crime were never found in unemployment, and unemployment never in crime, the coefficient of correlation would be -1, indicating a perfect inverse relationship. A coefficient of 0 would indicate that there is no relationship. The coefficient of .47 would accordingly indicate a significant but not a “high” correlation between crime and unemployment.

We cannot consider here all the details of statistical methods, but attention may be called to a few of the more significant features of the process. Statistics is a science, and consists in much more than the mere counting of cases.

With the collection of statistical data, only the first step has been taken. The statistics in that condition are only raw material showing nothing. They are not an instrument of investigation any more than a kiln of bricks is a monument of architecture. They need to be arranged, classified, tabulated, and brought into connection with other statistics by the statistician. Then only do they become an instrument of investigation, just as a tool is nothing more than a mass of wood or metal, except in the hands of a skilled workman.

The essential steps in a statistical investigation are: (1) the collection of material, (2) its tabulation, (3) the summary, and (4) a critical examination of the results. The terms are almost self-explanatory. There are, however, several general points of method to be noted.

In the collection of data a wide field must be covered, to be sure that we are dealing with invariable relations instead of with mere coincidences, “or overemphasizing the importance of one out of a number of cooeperating causes.” Tabulation of the data collected is very important, since classification of the data does much to suggest the causal relations sought. The headings under which data will be collected depend on the purposes of the investigation. In general, statistics can suggest generalizations, rather than establish them. They indicate probability, not invariable relation.

SCIENCE AS AN INSTRUMENT OF HUMAN PROGRESS. We have, in an earlier section of this chapter, referred to the practical value of science. “Man’s power of deliberate control of his own affairs depends upon ability to direct energies to use; an ability which is, in turn, dependent upon insight into nature’s processes. Whatever natural science may be for the specialist,... it is knowledge of the conditions of human action." And the wider, the more complete and the more penetrating our knowledge of the world in which we live, the more extended become the boundaries of human action. Through a knowledge of natural processes, men have passed from a frightened subjection to Nature to its conscious control. And the fruits of that control are, as we have already had occasion to notice, all-pervading in practical life. That complete transformation of life known as the Industrial Revolution, which came about with such swiftness and completeness in the early nineteenth century, and whose effects have not yet ceased to accumulate, was the direct outcome of the application of the experimental science which had begun in the sixteenth. Some of the consequences of the application of theoretical investigation to practical life have already been noted. There are first the more obvious facts of the inventions, great and small the railways, steamships, electric transportation, automobiles, and telephones which have changed in countless details our daily life. There are the profound and all-pervasive changes which have been brought about in industrial and social relations: the building-up of our vast industrial centers, the change from small-scale handicrafts to large-scale machine production, the factory system, with its concomitants of immensely increased resources and immensely complicated problems of human life. Science in the short span of three centuries has shown how rapid and immediate could be the fruits of human control of Nature, and its further fruits are incalculable.

Science has indeed already begun to affect men’s attitude towards experience as well as their material progress. It is only when men set out with the conscious realization that intelligence does make a difference in the world, that science becomes articulate. Science is the guarantee of progress. It has shown men that the future is to some extent in their own hands; that by dint of a laborious and detailed application of intelligence to the processes of nature, those processes can be controlled in the interests of human welfare.

Science has led men to look to the future instead of the past. The coincidence of the ideal of progress with the advance of science is not a mere coincidence. Before this advance men placed the golden age in remote antiquity. Now they face the future with a firm belief that intelligence properly used can do away with evils once thought inevitable. To subjugate devastating disease is no longer a dream; the hope of abolishing poverty is not Utopian.

But science may be used for any end. It reveals the relations of phenomena, relations which hold for all men. It shows what causes are connected with what consequents, and, as already pointed out, in the knowledge of causes lies the possible control of effects. We can secure the results we desire, by discovering what antecedents must first be established. Science is thus a fund of common resources. Specific causes are revealed to be connected with specific effects, and men, by making a choice of antecedents, can secure the consequences they desire. But which effects they will desire depends on the instincts, standards, and habits of the individual, and the traditions and ideals of the group. A knowledge of chemistry may be used for productive industrial processes, or in the invention of poison gas. Expert acquaintance with psychology and educational methods may be used to impress upon a nation an arbitrary type of life (an accusation justly brought against the Prussian educational system), or to promote the specific possibilities that each individual displays.

Not only are the fruits of scientific inquiry used in different ways by different individuals and groups, but scientific inquiry is itself affected by the prevailing interests and mode of life. What inquiries shall be furthered depends on what the individual or group feels it important to know. From a social point of view, certain scientific developments are of more urgency and imperativeness than others. During an emergency, as during the Great War, it might be necessary to turn all the energies of scientific men into immediately productive pursuits. And, since the pursuit of inquiry on a large scale demands large resources, those researches which give promise of beneficent human consequences will the more readily command social sanction and approval and will be developed at the expense of more remote speculations however intrinsically interesting these latter may be.

Science has proved so valuable a human instrument that it has attained a moral responsibility. Men have increasingly come to realize that the pressing problems of our industrial life require for their solution not the confusions and incompétences of passion and prejudice, but an application of the fruits of scientific inquiry. Science has already so completely demonstrated its vast fruitfulness in human welfare, that it must be watched with jealous vigilance. It must result as it began, in the improvement of human welfare. But what constitutes human welfare is a question which leads us into the final activity of the Career of Reason, Morals and Moral Valuation, man’s attempt to determine what happiness is, and how he may attain it.