We may even use two contradictory conceptual schemes, choosing one or the other at convenience, or from habit. We are all of us educated out of the old Ptolemaic conceptual scheme, which saw the sun moving about a stationary earth, into the Copernican conceptual scheme, which sees the earth moving about a stationary sun. Einstein, of course, used a conceptual scheme different from both of these, but most of us are not yet up to Einstein; in daily life we all, however, contentedly say “the sun rises,” and should be very pedantic indeed if we insisted on saying in Copernican terms “the earth has revolved into sight of the sun.” More important is the present situation in respect to conceptual schemes in modern physics. We learn, as far as laymen can learn in such matters, that physicists find it convenient in the study of certain problems to regard the electron as a particle, or at least a point, and in the study of other problems to regard it as a wave. Some physicists, many of them of very great distinction indeed, are troubled by this contradiction, and have sought to work out a single conceptual scheme which will make the electron a nice logical unity again. One suspects, however, that these physicists have left in them a little of the philosopher, and that it is their philosophical selves that demand unity in the electron. For other physicists get on admirably with this logically impossible electron, wave when they want it to be a wave, particle when they want it to be a particle. As scientists, they are quite content to solve their problems, which deal wholly with this world and can be solved in this world, though no doubt not in the next, without regard for ultimate truth.
The scientist, then, goes to work roughly in some such fashion as this: he starts with a conceptual scheme of some sort, and questions, or even hypotheses, he frames in terms of that scheme; he then hunts for a suitable supply of facts--and a fact in the natural sciences we define with Professor L. J. Henderson as “an empirically verifiable statement about phenomena in terms of a conceptual scheme”; these facts he seeks to arrange in uniformities or theories which will answer his questions, and perhaps suggest other questions; he then immerses himself again in the hunt for facts, and emerges with new or modified uniformities. The scientist is not interested in where his conceptual scheme came from, or whether it preceded or followed on facts, or whether it is “subjective” and the facts “objective.” These questions he leaves to the philosophers, who have not settled them yet after two thousand years of debate. But the scientist does, by his recognition that a conceptual scheme is as essential to his activity as are observed facts, emancipate himself completely from self-styled “scientific” materialists, positivists, empiricists, who naively assert that our sense-perceptions are somehow in themselves an orderly and sole reality, or a “reflection” of such a reality. For, note particularly, the facts with which the scientist deals are not phenomena, sense-perceptions, the “external world,” those dear absolutes of innocent positivists, but merely statements about phenomena. A properly verifiable statement about Cromwell is then as much a fact as the reading of a thermometer in a laboratory.
Fourth, though the scientist is very careful indeed about matters of definition, and is as disdainful of sloppiness and bad thinking as any logician can be, he distrusts rigidity and attempts at perfection here as elsewhere. He is interested less in beauty and neatness of definition than in having his definitions fit not his sentiments and aspirations, but the facts. Above all, he does not dispute over words. He is less interested in the accurate theoretical distinction between a mountain and a hill than he is in making sure that he is dealing with concrete elevations on this earth. He does not expect class-terms to be perfect, mutually exclusive; when he distinguishes between a plant and an animal, he is not at all offended if you call his attention to a living thing that seems to belong to both his classes at once. He sets to work studying the living thing and will, if necessary, modify his class-terms. But he is quite willing also, if it proves more convenient, to set up a new class-term of borderline plant-animals. This simple willingness to be guided by convenience is of course one of the amazing things about the scientist and one of the most difficult for us who have not had a scientific training to adapt ourselves to. Most of us are early trained to prefer our opinions to our convenience.
Finally, scientific thinking cannot be, except perhaps in suggesting problems, what nowadays most of us know well enough as wishful thinking. The scientist’s own hopes and fears, his own standards of what he would like to have prevail on this earth, must be kept as far as possible out of his work, and especially out of his observations of, or dealings with, facts. How far such hopes and fears and standards enter into his choice of conceptual schemes, how far they influence the kind of questions he asks, are difficult problems we may perhaps be permitted to dodge. Sufficient that the techniques of most of the established sciences provide a very effective check on the cruder forms of wishful thinking. History--because it has been so long an art and a craft perhaps the most respectable of the social sciences--provides in the technical training undergone by most professional historians a surprisingly effective and not wholly dissimilar check on the more violent forms of partisan writing and thinking.
All in all, there is no reason why we should feel that the natural scientist uses methods, sets standards, forever quite unattainable by the social scientist. Natural science as the more innocent materialists of the last century saw it--exact, infallible, a cosmos built on induction--must seem remote to a struggling economist or sociologist. But natural science as it has always been understood by its ablest practitioners and is now widely understood--natural science as expounded methodologically by a Poincaré--is no such thin substitute for Divine Providence, no such metaphysical abstraction. Only God is exact, infallible, omniscient, unchanging, and modern science has been content to leave the search for God to disciplines fitted by long success for such a search.
_III. The Application of Scientific Methods to This Study_
Of the bare elements of scientific thinking--conceptual scheme, facts, logical operations, uniformities--the social sciences in general come out well on the score of facts. Even in the field of history, where neither laboratory nor questionnaire methods of research are available, our existing supply of facts is surprisingly good. You cannot draw Cromwell back to life, but neither can you call the dinosaurs back to life. What we know about Cromwell is in many ways as reliable as what we know about dinosaurs. To say that history is a fable agreed upon, or a set of tricks played upon the dead, is to slander, or at least to misjudge, the great body of industrious and sober workers who have carried on the study of history. Notably the last century or so has seen the formation of a body of research workers in history who, with all their faults, maintain standards comparable in some ways to those maintained by similar groups in the natural sciences. These research workers do not indeed uncover the simple raw material of facts. The humblest antiquarian arranges the facts he digs out of his documents into some kind of pattern. Such a process of arrangement, however, is not the conscious theorizing of the physical scientist. It was never even learned as the scientist learns the theoretical scaffolding of his science, but was acquired almost as the manual worker acquires a craft. It is this craftsman’s technique for the gathering, winnowing, and assaying of facts about the behavior of men in the past that is the great strength of the professional historian. If you asked such a historian what a fact is, he would probably be greatly puzzled at the question, and usually quite unable to answer in adequate general terms. Any good philosopher could convict him of complete epistemological _naïveté_. But in his daily work the historian shows a very keen appreciation of the difference between a fact and a theory, and a real ability to manipulate and arrange facts.
We shall, then, rely on the historians to supply us with the necessary facts. For the English, American, and even for the French, revolutions, the body of reputable and reasonably detached historical writing is very large indeed. Passions still run high over the French revolution, but they are being cooled slowly in an increasing flood of printer’s ink; the chief trouble, indeed, is to choose from among this enormous mass of material. The Russian revolution is still too near us to be regarded by professional historians as capable of the kind of treatment the guild likes to give. Its source material is scattered about, and much of it is still withheld from scholars. Language is a barrier only gradually being overcome here in the West. Yet our supply of facts about the Russian revolution is by no means so slight, or so poor in quality, as to hinder our enterprise. Twenty years is a long time, and the early stages of the Russian revolution have been surveyed, if not _sine ira et studio_, at least with relative detachment. And then both lovers and haters of the present regime in Russia are almost equally articulate, and can be balanced off one against the other by anyone who cares to take the trouble.