It is proposed to examine the consequences which ensue if philosophy is deliberately oriented around the methods and results of science. That such reorientation has been more or less unconsciously taking place for centuries is evident; the problem demands particular discussion at this time only because the reorientation has gone so far and with such success as to challenge seriously certain past conceptions of philosophy and to demand of philosophers what, if anything, is left for them to do. For present purposes the revolution indicated will be regarded as a fait accompli, and the sole concern will be with what alternatives remain open. The conclusions differ from those of certain others who accept the same fait accompli only in believing that more alternatives do in fact remain open than they envisage.

What is metaphysics? There is real danger of taking the meaning of this term too much for granted, and of leaning too heavily upon an undefined word in the very act of dismissing metaphysics as word jugglery. Metaphysics is not, as I conceive it, the study of the wholly transcendent or supersensible. It may sometimes have been so conceived, and this is, indeed, one reason why some of its alleged results are so unsatisfactory—or, as positivists would say, meaningless. Such a meaningless “metaphysical” idea is the mediaeval doctrine of God as a power acting upon the world but not reacted upon by it, as purposive but non-temporal, loving but “impassive,” etc. Such is the windowless monad of Leibniz, connected with other monads only by pre-established harmony. Such is the Aristotelian idea of substance as that in which other things inhere but which itself is in nothing (apparently not even in the world or nature). The history of metaphysics is, indeed, strewn with failures to achieve meaning. But does this mean that metaphysics has scored no successes? Surely we must remember that human success is invariably of the fumble-and-correction type. Ideas such as those mentioned may be meaningless as they stand, and yet have potential meaning in that some modification of them might render them significant conceptions. We must also remember that mankind now possesses new instruments of logical analysis, and that these instruments may prove useful in metaphysics—not, as logical positivism holds, with the result of banishing all metaphysical ideas, but of correcting their erroneous aspects.

The general concept of a causal system has been basic in scientific thought. It may be formulated as follows. The system in question possesses certain measurable attributes such as those of dimensions, temperature, and so forth. In the case of a causal system, it is affirmed that the subsequent development of the system from a known initial condition—that is, a condition in which the measurable variables have known values—is uniquely determined by these values. More definitely, the value of these same variables after any interval of time depends only on the initial values of the variables and the time interval which has elapsed.

We pause in the process of exposition to note what continuity we may in the progress of the theories of discontinuity we have been discussing. The following trends are rather distinct: (1) the development of more and more general mathematical approaches, (2) a marked broadening of the field of experimental issues, and (3) an increasing attention to analysis of fundamental concepts, the philosophy of physics.

The species concept is one of the oldest and most fundamental in biology. And yet it is almost universally conceded that no satisfactory definition of what constitutes a species has ever been proposed. The present article is devoted to an attempt to review the status of the problem from a methodological point of view. Since the species is one of the many taxonomic categories, the question of the nature of these categories in general needs to be entered into.

In this paper I am going to try to indicate my notion concerning the nature and subject-matter of psychology. I am a behaviorist. I hold that psychology does not seek descriptions and intercommunications concerning immediate experience per se. Such descriptions and attempts at direct intercommunications may be left to the arts and to metaphysics. Psychology seeks, rather, the objectively stateable laws and processes governing behavior. Organisms, human and sub-human, come up against environmental stimulus situations and to these stimulus situations they, after longer or shorter intervals of time, behave. The laws and processes determining this their behavior are stateable in objective terms. Even in the cases where the organism is oneself, these determining causal factors can and must—for the purposes of psychology—be stated objectively. It is true that in these latter instances, in which the animal in question is oneself, one may in one's rôle, not of a psychologist, but of an artist or a metaphysician, attempt to describe and convey to another man one's own facts of immediate experience. But such a description and report of immediate experiences, except in so far as this report is itself a form of behavior and therefore like all other behaviors the basis for an investigation of the objective laws and processes underlying it, essentially new to the picture. Experience qua experience, while of concern and interest to the man in the street, the philosopher and the poet, does not enter as such into the laws and equations of psychology,—in so far, at any rate, as psychology is to be considered as a science.