Often scholars who call themselves social scientists have not meant by the term science the sort of activity which has generally concerned those calling themselves natural scientists. In the latter sense very little of what has been called “social science” can also be called scientific. The term “social science” as used here refers primarily to the studies which have gone under such titles as Politics (or Government, or Political Science), Sociology, Anthropology, Social and Clinical Psychology, and Economics. To some degree much of what will here be said does not apply with equal justice to the field of Economics. It has a more highly developed system of general abstractions and considerably more precise techniques of analysis than have generally characterized the other social sciences. The difference, however, is one of degree not kind. Many of the difficulties mentioned below certainly plague the field of Economics as well as the others.

Present-day logic regards definitions as syntactical devices of abbreviation. This view, summed up in the terse adage: “To define is to eliminate,” obscures the vital part played by definitions in deductive sciences. Abstract calculi, to become noetic tools, must be interpreted; so the richer the interpretation, the more efficient the tool. But most calculi are based on a restricted number of primitives; they thus embrace, at the outset, a restricted number of concepts and can be appraised through and only through the definitions they eventually yield. In a word, the richness of a calculus lies in its defining virtualities. The whole of PRINCIPIA MATHEMATICA would be a futile game of chess, did it not embody all our mathematical concepts; none of these being assumed as primitive, PRINCIPIA MATHEMATICA owes its momentous significance to its definitions and to its definitions only.

In a highly original and provocative essay entitled “Behavior, Purpose and Teleology”, published a few years ago, Professors Arturo Rosenblueth, Norbert Wiener and Julian Bigelow attempt to indicate the scientific importance and usefulness of the concepts of purpose and teleology. Since this essay appeared the suggestions it contains seem to have acquired a significance which was not wholly apparent at that time. This is due primarily to the fact that a somewhat novel and, it appears to some, revolutionary approach to certain problems has arisen in the sciences, an approach which is more or less loosely referred to as “cybernetics,” and among whose outstanding spokesmen are to be found the very authors of this essay—particularly Professor Wiener, whose recently published Cybernetics has been claiming the attention of an increasing number of scientists and non-scientists alike. In his book, it may be noted, Professor Wiener, in tracing the development of cybernetics over the past few years, gives a good indication of the importance he attaches to the earlier essay. He writes, with reference to it: “The three of us [Rosenblueth, Wiener and Bigelow] felt that this new point of view merited a paper, which we wrote up and published. Dr. Rosenblueth and I foresaw that the paper could only be a statement of program for a large body of experimental work, and we decided that if we could ever bring our plan for an interscientific institute to fruition, this topic would furnish an almost ideal center for our activity” (p. 15). It would seem, then, that an examination of the contents of this essay should not be without interest at this time.

In a recent essay (1) Professor Taylor criticizes the criteria used by Rosenblueth, Wiener and Bigelow in 1943 (2) to distinguish purposeful from non-purposeful behavior. He also criticizes our definition of behavior, our concept of the vague as opposed to the general, our use of the word correlation, and our statement that a system may reach a final condition. Indeed, there seems to be little, if anything, in our paper to which he does not emphatically object.

He maintains that the notions of purpose and teleology are not only useless for the understanding of mechanical behavior, but wholly incongruous when applied to this behavior. He further affirms that our use of the term purpose “bears no similarity whatever to the meaning which is ordinarily attached to it.” He does not state, however, his own notions of purpose and teleology; and the meaning which he considers to be ordinarily attached to the term purpose. This omission weakens his criticism considerably.

In their penetrating and admirably lucid discussion, “Purposeful and Non-purposeful Behavior,” Professors Rosenblueth and Wiener have considerably clarified the point of view expressed in their earlier paper dealing with the conception of purpose, and recently criticized by me. But while their discussion thus removes some of the difficulties which, I think, stood in the way of acceptance of their position, there yet remain fundamental questions which I do not believe have been adequately dealt with.

These authors rebuke me, with justice, for not indicating my own conception of purposiveness, and they add that this omission weakens my criticisms of their view. That the omission detracts from the interest of my paper is doubtless correct, but that it weakens my criticisms of their position is not similarly obvious. I shall, at any rate, attempt to rectify this defect in the present discussion.

In mathematics we have demonstrably insoluble problems, one example being that of trisecting an arbitrary angle in elementary geometry. Every now and then, we encounter engineers and others who offer solutions of the insoluble and make some stir. To those who feel convinced of the demonstration of insolubility, these claimed solutions do not seem to deserve any serious considerations. In fact, such solutions have long since ceased to attract attention from mathematicians.

The situation in philosophy seems different. Here we do not possess demonstrations as clear and distinct as in mathematics. For example, it has been a fashion among philosophers for two centuries or so to answer Hume's scepticism concerning induction. Although, presumably, there never has been any answer or solution which is as widely accepted among philosophers as Hume's sceptical argument, yet philosophers continue to enjoy elaborating arguments for and against Hume's scepticism. And people who feel convinced by Hume's resaoning often find it difficult to understand why philosophers persist in trying to contradict Hume flatly instead of seeking for some more devious way out.

The contention of the above comment, as I understand it, is that there is, analogously to the problem of trisecting an arbitrary angle in mathematics, a sound demonstration, along the lines employed by Hume and Russell, of skeptical conclusions concerning our inductive knowledge of the future, and that hence one is mistaken in imputing to that argument, as I have done, a logical slip arising from a confusion in the use of ‘future’ and other similar words. I am indebted to Mr. Wang for the stimulation, and to the Editor of Philosophy of Science for the opportunity, to try to make my points clearer.

The proponents of these skeptical arguments maintain that, apart from some supporting postulates which we must make in inductions about the future, we have no evidence concerning the future of any given moment. If we restrict ourselves to the evidence we have from the present and the past, and do not bolster this evidence with some Principle of Induction, like that of Hume to the effect that the future will be like the past, “we have no theoretical assurance,” as Mr. Wang puts it, “that the practice of guiding our activities by what we learn from ... [the past] will lead to success on the whole and in the long run.”

There has recently been considerable controversy in the literature over the concept “disposition to respond” as used by Charles Morris in his criterion by which it is to be determined whether or not something functions as a sign. It is often assumed that this concept serves as a means for broadening a strictly behavioral criterion through the introduction of something which is a characteristic of sign situations when behavior is not. But dispositions have no practical value in this respect, for Morris's criterion can not be used to obtain sign knowledge about situations not giving rise to overt behavior. However, dispositions do have a practical function in Morris's criterion, a function which has been overlooked in these discussions.