tion, feeling and volition. Here we have the soul as an organized whole; the whole antecedent history of consciousness expresses itself in the acts of apperception.—Wundt places increasing emphasis upon this activity in his later writings, and the concept of volition becomes his fundamental psychological concept so that (borrowing an expression of Paulsen's) he can describe his theory as voluntarism.
The epistemological motive which induced Wundt to enter the field of philosophy resulted from his recognition of the fact that all natural science rests upon certain presuppositions which condition all our knowledge (Die physikalischen Axiome und ihre Beziehung zum Kausalprinzip, 1866). Later on he elaborated his theory of knowledge partly in his Logik (1880-1883) and partly in his System der Philosophie (1887). Knowledge always begins with the conviction of the reality of our ideas. This naive realism breaks down however even by the necessity of distinguishing between sense perception, memory and imagination, and still more by scientific reflection, until it gradually yields to critical realism which substitutes object concepts which remain constant for the changing content of direct perception. In the sphere of sense perception the laws of space and time are elaborated as the expression of constant forms; in the sphere of intellectual knowledge the qualities immediately given are replaced by the concept of the object in the form of quantitative distinctions alone (spatial and temporal), whilst the psychical processes are referred to a fundamental spiritual activity. But rational knowledge, which demands a completion of knowledge by the idea of totality, carries us even farther than this. Such conclusion assumes the character of materialism whenever
