CONTRIBUTION TO THE THEORY OF SCIENCE 221 



Only activity of the latter forms our experiences or the content of our 

 consciousness. The participation of the former may call forth cor- 

 responding 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 par- 

 ticularly 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 repe- 

 tition of similar experiences (for instance the sequence of day and 

 night), we have become familiar with the interdependence of certain ex- 

 periences, 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 expecta- 

 tion 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 scien- 

 tific 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 ob- 

 servations of the position of a planet, is able to foretell its future posi- 

 tion. He is able to do so for a future the more remote the more ac- 

 curate his original observations. All such scientific predictions are 

 limited in regard to their content and exactness. If the skull pre- 

 sented • to the zoologist be that of a fowl, he is able to state the 

 characteristics of fowls in general, perhaps too whether this par- 

 ticular 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 ex- 

 tent, 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 — 



