It now becomes necessary to review that period of Dewey's philosophical career which is marked by the definite abandonment of the idealistic standpoint, and the adoption of the method of instrumental pragmatism. It has already been seen that there is a close connection between the "functionalism" which now begins to appear, and the "Psychological Standpoint" set forth in the preceding pages of this review. It is not possible, however, to account for all the elements which contribute to this development. Dewey was active in many fields and received suggestions from many sources. It seems best, in dealing with this period, to "follow the lead of the subject-matter" and avoid _a priori_ speculation on the factors which determined the precise form of Dewey's mature standpoint in philosophy. Dewey had always kept in mind the idea that the synthetic activity whereby self-consciousness evolves the ideality of the world must operate through the human organism. He had frequently referred to Green's saying that the Eternal Self-Consciousness reproduces itself in man, and to similar notions in Caird and Kant; but he had never considered, in a detailed way, how the organism might serve as the vehicle for such a process. His ethical theory, with its analysis of individuality into capacity and environment, tended to bring the body-world relationship into the foreground, and the idea that theory is relative to action tended to emphasize still more the relation of thought to the bodily processes. Dewey finally discovers the basis upon which the synthetic activity of the self, the thought process, may be described empirically and concretely. Organism-in-relation-to-environment becomes the key-stone of his theory of knowledge. Thought is interpreted as a function of the organism, biologically considered, and the biological psychology which results from this mode of interpretation is commonly known as 'functional psychology.' The functional psychology is presented in a series of articles in the _Philosophical Review_ and the _Psychological Review_, published between 1894 and 1898. The most important of these is "The Reflex Arc Concept in Psychology," published in the _Psychological Review_ in 1896.[116] Since it is the only article in the series which gives a complete view of the theory, it will be made the basis for the discussion of the functional theory of psychology.