This paper is concerned with a question in metaphysics. The question is: Is the world ultimately one, or is it many? It is neither a very profound nor a very complicated question. It is, on the contrary, very simple. But despite its simplicity, it expresses the most basic of all metaphysical problems.

When two metaphysical problems, A and B, are so related that the statement of B assumes an answer to A, then we may fairly infer that A is more basic than B, and B less basic than A.

Any physical theory which seriously proposes that events in the future may be the efficient causes of events in the past certainly may be regarded—at least at first glance—as a rather revolutionary doctrine. In a recent issue of the Reviews of Modern Physics (Vol. 17, Nos. 2 & 3, p. 157) commemorating Niels Bohr's sixtieth birthday, and under the editorship of the latest Nobel Prize winner in physics, W. Pauli, there appeared such a theory—written by Bohr's former student, J. A. Wheeler and Wheeler's associate (and former student) at Princeton, R. P. Feynman. The title of their paper appears harmless enough: “Interaction with the Absorber as the Mechanism of Radiation.” It is one part of a more comprehensive three-part paper intended for later publication as a general constructive critique of classical field theory (Maxwell's electrodynamics) and of the theory of action at a distance as propounded by Schwarzschild and Fokker. (In passing, we note that in this more general paper there is derived the Frenkel solution of the old problem of infinite self-energy of the point-charge electron.)

At the beginning of the twentieth century, philosophy in America and England began to respond to the rumors of unrest and dissatisfaction which were under way at the close of the nineteenth century. Many contemporary thinkers, who have had occasion to look backward, have remarked on the dominance of idealism at the turn of the period. Montague says it was “rampant” and points to the organization of the St. Louis school by W. T. Harris, the purpose being a study of Hegelian thought. Lovejoy also remembers the total sweep of idealistic thought. “The metaphysics of the philosophical teachers whose influence was dominant in most of the American universities thirty-five years ago had one common and fundamental premise which was supposed to be established beyond the possibility of reasonable doubt; to question it was simply to betray one's want of a genuine initiation into philosophy. It was the proposition that, in Bradley's words, 'to be real, or even barely to exist, is to fall within sentience; sentient experience, in short, is reality, and what is not this is not real. There is no being or fact outside of that which is commonly called psychical existence.' As my first teacher in philosophy, George Holmes Howison, said, in summing up a memorable philosophical symposium in 1895: 'We are all agreed' in one 'great tenet;' which is 'the entire foundation of philosophy itself: the explanation of the world which maintains that the only thing absolutely real is mind; that all material and all temporal existences take their being from Consciousness that thinks and experiences; that out of consciousness they all issue, to the consciousness they are presented, and that presence to consciousness constitutes their entire reality.' With almost a whole generation of acute and powerful minds this passed for a virtual axiom.”

Ever since the beginning of the modern era of science, more than 300 years ago, the scipntist has been embarassed at times when he undertook to describe the scope and objectives of science. Part of this embarassment was due to the difficulty of setting up the scope and objectives in such a way as to leave room for future development, and at the same time to permit of seeing the limitations of science clearly and truthfully. Recently in an article “On the possible philosophies of science”, Professor Malisoff made use of the old practise in philosophical discussion of using conjugate terms. These terms as used are so selected that complementary pairs characterize or describe an entity or whole of some kind. The difficulty in describing the scope, objectives and especially the limitations of science, arises chiefly from the difficulty of establishing some simple entity that will contain all of this as well, as the remainders that must be included, and that involve the limitations of science, chiefly. This use of conjugate terms offered a solution of this difficulty.

It is a happy circumstance that this important aspect of method should be brought to our attention by a distinguished scientist in the field of biology. In the past any reference to the “psychical” by the scientific methodologist has been regarded as a dubious departure from his strict routine. But the recognition, finally, by a man of science, of the aleatory, autonomous character of a spontaneous universe, disclosed in biological directives as well as in the dynamics of the atom, is a stimulating enhancement of that philosophy which, as Dewey says, is “the critical theory of methods of criticism.”

This study is an attempt partially to describe the sociological foundations of modern science. When the question is put, under what social circumstances did the idea of science develop, one sees that there is here an inadequately explored sociological area. Perhaps a definition and a contrast will make this clearer. By the idea of science is meant simply the proposition that the valid source of human knowledge is to be found in the analysis of experience. But knowledge in this sense was not a problem in the medieval period. In the first place, it was then taken for granted that the universe was intelligible to man on the basis of divinely revealed principles. Secondly, man constituted the center of the universe, which in its entirety was thought to be subordinate to man's destiny. Thirdly, not only was the universe which existed for man then known by him, but it was endowed with human qualities. The categories of interpretation were substance, essence, form, matter, quality, and purpose. The reason why rain fell upon the earth was to grow crops; the purpose of the moon and the stars was to light the earth at night, and to act as guideposts for him on his travels. Bodies tended to their proper places, light ones upward, heavy ones earthward. Quantitative differences were inferred from these qualitative ones. It is well-known, for example, how tenaciously was the knowledge held, that heavier objects fall more quickly than lighter ones. And finally, the universe was religious. If the world existed for the benefit of man, man existed for the glory of God. Human sojourn upon the earth was merely preparation for permanent residence in eternity.

The use that the scientist makes of his principles is well known. In the normal course of scientific investigation, a hypothesis which explains some physical phenomenon adequately in every particular, but which runs counter to, say, the laws of inertia, cannot be held without further experimentation. Such experimentation must continue until the irreconcilability of the hypothesis with the laws is resolved. In most cases the hypothesis will fail to submit to further tests, will be declared inadequate, and will give way to a new one.