One of the annoying habits of philosophers is to substitute without warning a normative for a descriptive theory of the topic they are discussing—that is, in what purports to be a statement of how the subject actually presents itself they tell us instead how it ought to present itself. Current treatments of the elusive topic “meaning” seem to me to supply capital instances of this vice. Defenders of a positivist or an operational theory of meaning (I pick these two because of their wide contemporary influence) often give us no hint that their conclusions are conclusions about how the meaning of words ought to be interpreted, not about how, by and large, it is interpreted. Without such a hint their readers naturally suppose that it is the latter problem with which they are concerned, but this is rarely the case; were it so, emphasis could hardly fail to fall on determinants of meaning that are too often neglected by philosophical analysts.

Twenty five hundred years ago a Greek named Thales introduced something important into the world. We know little about the details, but there is a persistent tradition going back at least as far as Aristotle that Thales is to be given the credit for being the first person to think in the way that led, without break in continuity, to the development of the scientific method of thought. The conclusions to which Thales came, if we can trust the tradition, are of no value today. The important thing was the way of putting and answering questions. This was carried on by Thales' followers until by the time of Plato and Aristotle the essentials of the scientific method were coming to be recognized even though they were not explicitly and adequately stated in abstraction.

In one of its numerous meanings “mind” has long represented, and popularly still to some extent does represent, a special non-spatial type of entity transcending and ideally complementing the world of matter. More particularly it has stood for an innate “rational faculty” characterizing men as men; an immaterial substance radically differentiating human beings from animals and by the same token serving to bind them to one another, as brothers are bound by the tie of common blood. Thus conceived, mind traditionally has justified, and so strengthened, the ingenuous a priori regard and appreciation which unlearned persons extend to their fellows for the sole reason that they are human. Upon this conception of mind numerous popular doctrines of “personal dignity,” “human equality”, “individual liberty”, “freedom of conscience”, “inalienable rights”, and so forth, have been rationally grounded. And without it as an inspiration—to name but one dependent consequence—“the American dream”, which Adams describes in The Epic of America, would doubtless never have been dreamt.

The most satisfactory way of isolating the specific issues with which this paper is concerned is by way of a brief summary of the theory and its internal development. The development of the theory embodies two major movements. These are: (a) an analysis of what the author considers the typical perceptual experience, “a perceptual situation”, and (b) the projection of a theory of the physical world on the basis of the results derived. We may consider these in order.

A term and its contradictory exhaust the universe of discourse, but when examined for their relation to each other, I believe they are seen to exhaust that universe in a more particular respect than may have come into notice. They seem to exhaust or annul one of the leading notions of mathematical logic. This notion is the one concerning the whereabouts of the null class.

When the student of logic is first initiated into the problem of the relation of implication as expressed by the hypothetical proposition, he enters into a portion of logic which seems to him an impenetrable jungle. Elementary statements of the meaning of implication, as he is acquainted with them, are so meagre that they have failed to give any indication of the problems and paradoxes involved. Adequate discussions, on the other hand, are so abstruse that the initiate is lost in their incomprehensibility, for these are issues discussed by the technical logicians largely among themselves. When one considers the important bearings implicit in the interpretation of implication, such a state of affairs is greatly to be deplored. Through a simple but adequate presentation of the meaning of a hypothetical proposition one may be led not only to an understanding of a fundamental paradox of logic but to the whole question of modal logic and of the philosophy of logic. It is my purpose in what follows to present as simply as possible the various interpretations of the meaning of implication and to show their relations to modal logic. Having done this I believe it will be possible to state the case in favor of material implication in a new light.

Two distinct attitudes have been adopted by investigators in the field of the sociology of knowledge. One of them may be called speculative; the other, empirical. The central interest of an investigator having the speculative attitude lies in developing a theory of the sociology of knowledge. The central interest of investigators having the empirical attitude lies in finding out or explaining concrete phenomena; the theory is employed, implicitly or explicity, for this purpose. The existence of the two attitudes may be in part explained, as far as the German sociology of knowledge is concerned, by reference to the history of this school, which has grown out of and has been determined by a Marxist and materialistic philosophy, and especially by the use of this philosophy as a political instrument in the struggle of the emerging proletariat against the bourgeoisie. This statement, however, must be supplemented by a short location of the four most important contributors to the theory of the German sociology of knowledge. Max Scheler approaches the problem phenomenologically; he was the first and only one to ask the fundamental question, “What is knowledge?” Karl Mannheim, though markedly influenced by the Marxist viewpoint, particularly by Lukács, seems to me more adequately characterized by stressing his development from a more exclusively speculative to a more decidedly empirical attitude, which latter is especially evident in his most recent book, Man and Society in an Age of Reconstruction (1940). Alexander von Schelting's main contribution is his thorough logical analysis of Mannheim's theory in the light of Max Weber's methodology. Ernst Grünwald has given the most complete survey of the forerunners, the history, and the various contributions of the sociology of knowledge. These four thinkers are indirectly dependent on the historically determined emphasis of the movement on ideology in that they remain on the level of a theoretical discussion without arriving at factual research.

Social conflicts of ever widening scope have in recent years emphasized the importance of the problem of the relation of facts and values. This problem has received increasing attention from researchers and theorists in both the physical and social sciences. A number of interesting but by no means compatible solutions have been proposed.

Perhaps the simplest and most striking is the position of Carnap, Russell, and others, that value sentences, such as “A ought not to kill B” or “Killing is evil” are merely commands or expressions of wish and, as such, are emotional ejaculations or expletives but not statements which have any theoretical sense or enter (except as subject matter) into science. On this view the problem of the relation of fact and value statements is meaningless, or at least is not worth considering further.

Constitutional schemata have been of continuing interest in medicine and psychology ever since the time of Hippocrates. With the work of Sheldon, Stevens and Tucker (5, 6), biotypology has been placed on a new basis. The reader who wishes to orient himself quickly and without too much detail, to the subject matter of typology, will find an interesting and substantial review by Anastasi (1). Wertheimer and Hesketh (7) have produced a comprehensive, but brief, historical and analytic treatment of the constitutional approach in their rather short monograph on the subject. Hempel and Oppenehim (2) have examined the concept of psychological type in a novel fashion from the standpoint of modern logic and positivist philosophy. Typology has been of more interest to continental writers than to American writers. Numerous medical school dissertations at European universities attest to this fact. Medical and psychological literature on the subject is also more frequently of European or Latin American origin, than of United States origin, as a cursory glance at the Index Medicus (4) or the Surgeon General's Catalogue (3) will quickly reveal. The work of Sheldon has raised fresh theoretical considerations which we propose to outline to some extent in this paper and the above sources, we feel certain, will furnish sufficient orientation to those readers who come to this subject with little or no previous acquaintance with it. Before going any further the reader is urged to read Chapter V of the “Varieties of Human Physique” (5).