Science is not merely a collection of facts and formulas. It is preëminently a way of dealing with experience. The word may be appropriately used as a verb: one sciences, i.e., deals with experience according to certain assumptions and with certain techniques. Science is one of two basic ways of dealing with experience. The other is art. And this word, too, may appropriately be used as a verb; one may art as well as science. The purpose of science and art is one: to render experience intelligible, i.e., to assist man to adjust himself to his environment in order that he may live. But although working toward the same goal, science and art approach it from opposite directions. Science deals with particulars in terms of universals: Uncle Tom disappears in the mass of Negro slaves. Art deals with universals in terms of particulars: the whole gamut of Negro slavery confronts us in the person of Uncle Tom. Art and science thus grasp a common experience, or reality, by opposite but inseparable poles.

Since my discussion of an experimental arrangement of the sciences for certain practical objectives, some comment has appeared which makes it necessary to re-emphasize certain points by a further example. There seems to be something like a desire to paralyze the hand that makes arrangements for fear that undue profound metaphysical significance may be seen in a “mere” arrangement. It is the perennial fear of the a priori, the fear of a principle being invoked because of its “self-evidence”, and then turning traitor on the actual evidence. I invoke no such principle either overtly or covertly.

Like most other subjects under discussion today, the theory of nature is largely controlled by considerations of knowledge. Treatment of it is, consequently, incidental to the treatment of these other problems, and is undertaken, in the main, because they compel it. A brief catalogue of characteristic statements about nature will illustrate this. “Nature,” says one writer, “is that which we observe in perception through the senses”; and another writes, “It is not experience which is experienced, but nature—stones, plants, animals, diseases, health, temperature, electricity, and so on.” Nothing is more apparent in these sentences than the fact that it is not nature that the writers are so much concerned with, as with what it is that appears through the senses. The theory of nature, that is, is not so much guided by an analysis of the word's context and usage, as it is by the question: what is the proper object of knowledge? Consequently it is the latter question that is answered and not the question: what is nature? The reason for this is evident in the purpose of these statements and in their history; their purpose: the desire to do away with the separation between experience and nature, and to transform nature into a field familiar and accessible; and their history: the very framework against which they are directed, for they are embedded in the set-up from which they are trying to disentangle themselves. Perhaps something ought to be said to substantiate the thesis that the sentences cited are controlled by the problem of knowledge, especially since their intent seems to be to escape that problem. In any case, their history should serve to clarify them, and render a different approach to the theory of nature more significant.

For the purposes of this paper, realism is defined as the belief that in visual perception there is a direct perception of material bodies existing in space external to the perceiver's body. Most contemporary positivists and analytical philosophers are realists in this sense. Included in this classification would be all those who argue from the character of seen relations of bodies to the uniformity view of causation; those who oppose public (extended or in space) to private experience; those who believe that one can point to facts; those who believe in the real existence of objects like extended solid tables and chairs; and those who distinguish in terms of verifiability between judgments of color and judgments of value.

There are some indications that the philosophy of science is reaching the age of discretion. Now, as I understand it, the age of discretion is characterized by self-examination. Youth is a period of blundering enthusiasm. But maturity demands the sobering influence of principles, perspectives and techniques. The adult must put away childish things. This does not demand the elimination of spontaneity and imagination, but it does require their chastening according to the principles of propriety. It seems time to ask ourselves whether the philosophy of science ought to be allowed henceforth just to grow, like Topsy, or whether a serious attempt ought not to be made to determine its nature and task.

There is a considerable divergence of opinion about the meaning of mathematics, and it is only with hesitation that I, as a theoretical physicist concerned mainly with geophysics, venture to discuss a matter that professional logicians differ about. Nevertheless I am concerned with the problems of the acquirement of knowledge by scientific methods, and the solutions of these problems involve pure mathematics, the validity of which one is usually willing to take for granted. But the logical schools are not so willing, and aim at demonstration. Logic must be true in all possible worlds, and all empirical propositions must be rigorously excluded. A scientist, on the other hand, is interested mainly in empirical propositions, and mathematics (with logic) is primarily a tool for investigating their relations. The proof of mathematics would therefore have interest for science, provided that the proof is sufficiently general to cover scientific requirements. If it is not, and the subject matter of the proof is restricted so that it fails to cover the scientific use of mathematics, then in its scientific application it is merely an analogy, and we are no better off than we should be if we simply took the validity of mathematics as it stands as a postulate.

The modern theoretical physicist is a strange creature. Perhaps in every age the theoretical physicist has seemed so to his contemporaries who took the trouble to observe and think about him. There seems, for example, something almost too magical in the uncanny way in which he pulls a brand new atomic particle out of a theory, a way that reminds us of a rabbit being produced out of a hat. This is usually done in an off-hand manner with a considerable amount of patter of a highly abstract symbolic character but with a few words inserted in the right places for the benefit of the experimental physicist and a final prediction that if the experimenter does thus and so in the laboratory he will find a certain result. No wonder the observer marvels when the answer comes out right. But as he thinks further he is inclined to wonder whether it is necessary or desirable for the details of the process which led to the result to be so unintelligible. For unintelligible they seem to be to a great many people who are directly concerned with their understanding, to the people who for years have been laboring under the belief that they are engaged in the task of finding out how Nature works. What is this curious process whose whole task, according to one distinguished exponent of it, is merely to predict experimental results, and what is its future likely to be? These are the questions we are setting for ourselves in the present discussion. It is unlikely that the answers given here will satisfy everybody, but it is reasonably certain that nobody who aspires to an interest in science can fail to attach some meaning to them whether or not he agrees.

The widespread publicity and the consequent furor created by Dr. J. B. Rhine's experiments on telepathy and clairvoyance, have been interpreted in some quarters as a call for a thorough-going revision of the entire field of psychological thought. This revision, it is held, must be in the direction of philosophic idealism, and away from previously accepted materialistic doctrines. The present paper points out the non-verifiable nature of the entities postulated by the believers in “supernormal” phenomena. Furthermore, the interpretations of contemporary science held by such individuals are not in themselves on a scientific plane. Specific errors in reasoning made by workers in the field of psychical research, are presented. In short, “psychical research … cannot turn the universe into a non-material, non-objective one, on either the basis of misinterpretations of current physical thought or on the basis of its own work.”

Encyclopaedism” is the systematically pursued activity within the Unity of Science Movement, devoted to the collecting of scientific statements of the logic of science (synonymous with “Philosophy of Science” for Carnap and other representatives of modern Logical Empiricism) logic, mathematics, physics, biology and other sciences, including all the “cross connections” between the given disciplines. (See: Otto Neurath, Unified Science as Encyclopedic Integration; in: International Encyclopedia of Unified Science, Vol. I, No. I.)

It is impossible for us to understand the character of Newton or the state of the physical sciences in the seventeenth century, without referring at length to the life and work of Robert Hooke.’ So writes the author of a recent biography of Newton. Well might we ask with him ‘What manner of man was he whose personal opposition delayed the publication of Newton's Optics for thirty years and almost prevented the completion of the Principia; whose bitter tongue confirmed Newton's tendency to secrecy and isolation, destroyed his early enthusiasm for the Royal Society, and disgusted him with science?’ It is not surprising that a man, capable of all this, should play a conspicuous rôle in the history of natural philosophy. Indeed a study of Hooke's career throws much light on the origins of modern science and, in particular, it helps to determine the much disputed status of mathematics in the development of physical theory.