This form of non-voluntary reproduction is one of the best verified and most abundantly established facts in the whole realm of mental events. It permeates inseparably every form of reproduction, even the so-called voluntary form. The function of the conscious will, for example, in all the numerous reproductions of the syllable-series which we have come to know, is limited to the general purpose of reproduction and to laying hold of the first member of the series. The remaining members follow automatically, so to speak, and thereby fulfill the law that things which have occurred together in a given series are reproduced in the same order.
However, the mere recognition of these evident facts has naturally not been satisfying and the attempt has been made to penetrate into the inner mechanism of which they are the result. If for a moment we try to follow up this speculation concerning the Why, before we have gone more than two steps we are lost in obscurities and bump up against the limits of our knowledge of the How.
It is customary to appeal for the explanation of this form of association to the nature of the soul. Mental events, it is said, are not passive happenings but the acts of a subject. What is more natural than that this unitary being should bind together in a definite way the contents of his acts, themselves also unified? Whatever is experienced simultaneously or in immediate succession is conceived in one act of consciousness and by that very means its elements are united and the unison is naturally stronger in proportion to the number of times they are entwined by this bond of conscious unity. Whenever, now, by any chance one part only of such a related complex is revived, what else can it do than to attract to itself the remaining parts?
But this conception does not explain as much as it was intended to do. For the remaining parts of the complex are not merely drawn forth but they respond to the pull in an altogether definite direction. If the partial contents are united simply by the fact of their membership in a single conscious act and accordingly all in a similar fashion, how does it come about that a sequence of partial contents returns in precisely the same order and not in any chance combination? In order to make this intelligible, one can proceed in two ways.
