my body, is merely an object abstracted from an idea of my experience; and what is really known in every case is a unitary experience; divisible, but not separable, into body and soul, physical and psychical factors of one and the same unitary experience. Wundt is confined by his starting-point to his deduction that what we know is mental phenomena, ideas regarded as objects and subjects of experience.
With these four positions in hand, Wundt’s philosophy consecutively follows, beginning with his psychology. He begins with psychical elements, sensations and feelings, but he asserts that these always exist in a psychical compound, from which they can be discovered only by analysis and abstraction; and his paradox that a pure sensation is an abstraction is repeated by W. James. Further, Wundt declares that the psychical compound of sensations, with which, according to him, we actually start, is not a complex sensation, but a compound idea; so that I am expected to believe that, when I hear the chord of D, I am not conscious of single sensations of D, F, A, and have only a compound idea of the chord—as if the hearing of music were merely a series of ideas! Wundt, however, has a reason for substituting compound idea for sensation: he accepts Lotze’s hypothesis of local signs, and adds a hypothesis of temporal signs. He supposes that we have no sensations of space and time, as the nativists suppose, but that, while local signs give us spatial ideas, feelings of expectation are temporal signs giving us temporal ideas, and that these ideas enter into the psychical compound, which is our actual starting-point. It follows that every psychical compound into which temporal and spatial ideas enter must itself be an idea; and, as time at any rate accompanies all our sensations, it follows that every psychical compound of sensations, containing as it does, always temporal, if not also spatial, ideas, must be a compound idea, and not, as nativists suppose, Schuppe for instance, a compound sensation. The next question is, how compounded? Wundt’s answer is that inner impulsive will, in the form of passive apperception, forms compound ideas by association; so that all these operations are necessary to the starting-point. He prefixes to the ordinary associations, which descend from Hume, an association which he calls fusion (Verschmelzung), and supposes that it is a fundamental process of fusing sensations with spatial and temporal ideas into a compound idea. But he also recognizes association by similarity, or assimilation, or “apperception” in Herbart’s more confined sense of the word, and association by contiguity, or complication. Recognizing, then, three kinds of association in all, he supposes that they are the first processes, by which inner will, in the form of passive apperception, generates ideas from sense. So far his psychology is a further development of Hume’s. But he does not agree with Hume that mind is nothing but sensations, ideas, and associations, but with Kant, that there are higher combinations. According to him, inner decisive will, rising to active apperception, proceeds to what he calls “apperceptive combinations” (Apperceptionverbindungen); first to simple combinations of relating and comparing, and then to complex combinations of synthesis and analysis in imagination and understanding; in consequence of which synthesis issues in an aggregate idea (Gesammtvorstellung), and then at last analysis, by dividing an aggregate idea into subject and predicate, forms a judgment (see further Logic). The main point of this theory is that, if it were true, we should be for ever confined to a jumble of ideas. Wundt, indeed, is aware of the consequences. If judgment is an analysis of an aggregate idea into subject and predicate, it follows, as he says, that “as judgment is an immediate, so is inference a mediate, reference of the members of any aggregate of ideas to one another” (System der Philosophie, 66, first ed.). He cannot allow any inference of things beyond ideas. His psychology poisons his logic.
In his logic, and especially in his epistemology, Wundt appears as a mediator between Hume and Kant, but with more leaning to the latter. While he regards association as lying at the basis of all knowledge, he does not think it sufficient, and objects to Hume that he does not account for necessity, nor for substance and causation as known in the sciences. He accepts on the whole the system of synthetic understanding which Kant superimposed on mere association. Yet he will not proceed to the length of Kant’s transcendentalism. Between Hume’s a posteriori and Kant’s a priori hypothesis he proposes a logical theory of the origin of notions beyond experience. He explains that the arrangement of facts requires “general supplementary notions (Hülfsbegriffe), which are not contained in experience itself, but are gained by a process of logical treatment of this experience.” Of these supplementary notions he holds that the most general is that of causality, coming from the necessity of thought that all our experiences shall be arranged according to ground and consequent. That sense only gives to experience coexistences and sequences of appearances, as Hume said and Kant allowed, is also Wundt’s starting-point. How then do we arrive at causality? Not, says Wundt, by association, as Hume said, but by thinking; not, however, by a priori thinking, as Kant said, but by logical thinking, by applying the logical principle of ground and consequent (which Leibnitz had called the principle of sufficient reason) as a causal law to empirical appearances. Now, Wundt is aware that this is not always possible, for he holds that the logical principle of ground belongs generally to the connexion of thoughts, the causal law to the combination of empirical appearances. Nevertheless he believes that, when we can apply measures to the combination of empirical appearances, then we can apply the logical principle as causal law to this combination, and say that one appearance is the cause of another, thus adding a notion of causality not contained in the actual observations, but specializing the general notion of causality. He quotes as an instance that Newton in this way added to the planetary appearances contained in Kepler’s laws the gravitation of the planets to the sun, as a notion of causality not contained in the appearances, and thus discovered that gravitation is the cause of the appearances. But Newton had already discovered beforehand in the mechanics of terrestrial bodies that gravitation constantly causes similar facts on the earth, and did not derive that cause from any logical ground beyond experience, any more than he did the third law of motion. Wundt does not realize that, though we can often use a cause or real ground (principium essendi) as a logical ground (principium cognoscendi) for deducing effects, we can do so only when we have previously inferred from experience that that kind of cause does produce that kind of effect (see Logic). Otherwise, logical ground remains logical ground, as in any non-causal syllogism, such as the familiar one from “All men are mortal,” which causes me to know that I shall die, without telling me the cause of death. Wundt, however, having satisfied himself of the power of mere logical thought beyond experience, goes on to further apply his hypothesis, and supposes that, in dealing with the physical world, logical thinking having added to experience the “supplementary notion” of causality as the connexion of appearances which vary together, adds also the “supplementary notion” of substance as substratum of the connected appearances. But, using substance as he does always in the Kantian sense of permanent substratum beneath changing phenomena, and never in the Aristotelian sense of any distinct thing, he proceeds to make distinctions between the applications of causality and of substance. Even in the physical, he confines substance to matter, or what Aristotle would call material causes, thus makes its power to be merely passive, and limits substantial causality to potential energy, while he supposes that actual causality is a relation not of substances but of events. On this false abstraction Sigwart has made an excellent criticism in an appendix at the end of his Logic, where he remarks that we cannot isolate events from the substances of which they are attributes. Motions do not cause motions; one body moving causes another body to move: what we know is causal substances. Secondly, when Wundt comes to the psychical, he naturally infers from his narrow Kantian definition of substance that there is no proof of a substrate over and above all mental operations, and falsely thinks that he has proved that there is no substance mentally operating in the Aristotelian sense. Thirdly, on the grounds that logical thinking adds the notion of substance, as substrate, to experience of the physical, but not of the psychical, and that the most proper being of mind is will, he concludes that wills are not active substances, but substance-generating activities (“nicht thätige Substanzen sondern substanzerzeugende Thätigkeiten,” System, 429).
What kind of metaphysics, then, follows from this compound of psychology and epistemology? As with Kant against Hume, so with Wundt against Mach and Avenarius, the world we know will contain something more than mere complexes of sensations, more than pure experience: with Wundt it will be a world of real causes and some substances, constituted partly by experience and partly by logical thinking, or active inner will. But as with Kant, so with Wundt, this world will be only the richer, not the wider, for these notions of understanding; because they are only contributed to the original experience, and, being mentally contributed, only the more surely confine knowledge to experience of mental phenomena. Hence, according to Wundt, the world we know is still unitary experience, distinguished, not separated, into subject and object, aggregates of ideas analysed by judgment and combined by inference, an object of idea elaborated into causes and substances by logical thinking, at most a world of our ideas composed out of our sensations, and arranged under our categories of our understanding by our inner wills, or a world of our ideating wills; but nothing else. It is Wundt’s own statement of his solution of the epistemological problem “that on the one hand the whole outer world exists for us only in our ideas, and that on the other hand a consciousness without objects of idea is an empty abstraction which possesses no actuality” (System, 212–213). There remains his theory of reason. His pupil, Oswald Külpe (1862– ), who bases his Grundriss der Psychologie on the hypothesis of unitary experience, says in his Einleitung in die Philosophie (1895; 4th ed. 1907) that Wundt in his System derives the right of metaphysics to transcend experience from similar procedure
