1. The concept association has undergone, in the development of psychology, a necessary and very radical change in meaning. To be sure, this change has not been accepted everywhere, and the original meaning is still retained, especially by those psychologists who support, even today, the fundamental positions on which the association-psychologygrew up (§ 2, p. 13 sq.). This psychology is predominantly intellectualistic, pays attention to nothing but the ideational contents of consciousness and, according limits the concept of association to the combinations of ideas. Hartley and Hume, the two founders of association-psychology, spoke of "association of ideas" in this limited sense. [ 1 ] Ideas were regarded as objects, or at least as processes that could be repeated in consciousness with exactly same character as that in which they were present at first (p. 13, 8). This led to the view that association was a principle for the explanation of the so-called "reproduction" of ideas.
Furthermore, it was not considered necessary to account for the rise of composite ideas with the aid of psychological analysis, since it was assumed that the physical union of impressions in sense-perception was sufficient to explain the psychological composition and so the concept of association was limited to those forms of so-called reproduction in which the associated ideas succeed one another in time. For the discrimination of the chief forms of successive associations Aristotle's logical scheme for the memory-processes was accepted, and in accordance with the principle classification by opposites the following forms were discriminated: [p.
225] association by similarity and contrast, and association by simultaneity and succession. These class-concepts gained by a logical dichotomic process were dignified with the name of "law of associations". Modern psychology has generally sought to reduce the number of these laws. Contrast is as a special form of similarity, for only those concepts are associated which belong to the same class; and associations by simultaneity and succession included under contiguity. Contiguity is then regarded as outer association and contrasted with inner association by similarity. Some psychologists believe it possible to reduce two forms to a single, still more fundamental, "law of association" by making association by contiguity a special form of similarity what is still more common, by explaining similarity as a result of association by contiguity. In both cases association is generally brought under the more general idea of practice or habituation.
2. The whole foundation for this kind of theorizing is destroyed by two facts which force themselves irresistibly upon us as soon as we begin to study the matter experimentally.
The first of these facts is the general result of the psychological analysis of sense-perceptions, that composite ideas, which association-psychology regards as irreducible psychical units, are in fact the results of synthetic processes which are obviously in close interconnection with the processes commonly called associations. The second fact comes from the experimental investigation of memory-processes. It is found that the reproduction of ideas in the strict sense of a renewal in its unchanged form of an earlier idea, takes place at all, but that what really does happen of memory is the rise of a new idea in consciousness, always differing from the earlier idea to which it is referred, and deriving its elements as a rule from various preceding ideas. [p. 226]
It follows from the first fact that there are elementary processes of association between the components of ideas preceding the associations of composite ideas with one another which the name is generally limited. The second fact proves that ordinary associations can be nothing but complex products of such elementary associations. These can show the utter unjustifiableness of excluding the elementary processes whose products are simultaneous ideas rather than successive, from the concept association. Then, too, there no reason for limiting the concept to ideational processes. The existence of composite feelings, emotions, etc., shows, on the contrary, that affective elements also enter into regular combinations, which may in turn unite with associations of sensational elements to form complex products, as we saw in the rise of temporal ideas (§ 11, p. 156 sq.). The intimate relation between the various orders of combining processes and the necessity of elementary associations as antecedents to all complex combinations, furnishes further support for the observation made on the general mode of the occurrence of conscious processes, that it is never possible to draw a sharp boundary line between the combinations of the elements that compose psychical compounds, and the interconnection of the various psychical compounds, in consciousness (p. 203).