Only activity of the latter forms our experiences or the content of our consciousness. The participation of the former may call forth corresponding processes in the latter, though this is not always necessary. Our sensory apparatus may be influenced without our 'noticing' it, i. e., without the participation of the apparatus of thought. A particularly important reaction of the thought apparatus is 'memory,' i. e., the consciousness that an experience just taking place corresponds more or less with former experiences. It is the peculiar expression by the apparatus of thought of the general physiological law that every process influences an organ in such a way that it reacts to a repetition of this process in a way different from its reaction the first time, namely, by facilitating repetition. This effect decreases in time.
Upon these conditions experience in the abstract is based and is the result of the fact that experiences are composed of a whole series of simultaneous and successive components. If, as the result of the repetition of similar experiences (for instance the sequence of day and night), we have become familiar with the interdependence of certain experiences, we no longer perceive such an experience as an entirely new one, but rather as in part familiar, so that its separate parts or phases no longer astonish us. We anticipate or expect them. From expectation to prediction is but a very short step. Thus experience enables us to prophesy the future from the past and the present.
This is the path to science which is nothing other than experience systematized, that is to say, reduced to simple and comprehensible terms. Its aim is to predict from the known part of a phenomenon the part that has remained unknown. It matters not whether we have to deal with phenomena of space or of time. Thus from a skull the scientific zoologist is able to determine the animal; that is to say, he is able to state the nature of all the other parts of the animal to which the skull belonged. In the same way an astronomer on the basis of a few observations of the position of a planet, is able to foretell its future position. He is able to do so for a future the more remote the more accurate his original observations. All such scientific predictions are limited in regard to their content and exactness. If the skull presented to the zoologist be that of a fowl, he is able to state the characteristics of fowls in general, perhaps too whether this particular fowl possessed a comb or not. He will be unable to tell its color and only within wide limits its age or its size. Both facts, the possibility of prediction and its limitations as regards content and extent, are expressions of the fundamental fact that our experiences may be similar, but are never completely identical.
These preliminary considerations need to be explained and enlarged upon in various directions. One may object to calling a fowl or a planet an experience. We call them by the most universal name—
