ON THE THEORY OF SCIENCE 335 



decreases with the lapse of time. Further, we must consider the 

 fact mentioned above, that an experience is never exactly repeated, 

 and that therefore the " memory "-reaction occurs even where there 

 is only resemblance or partial agreement in place of complete agree- 

 ment. Here, too, there are different degrees; memory takes place 

 more easily the more perfectly the two experiences agree, and vice 

 versa. 



If we look at these phenomena from the physiological side, we 

 may say we have two kinds of apparatus or organs, one of which 

 does not depend upon our will, whereas the other does. The former 

 are the sense organs, the latter constitutes the organ of thought. 

 Only the activities of the latter constitute our experiences or the 

 content of our consciousness. 



The activities of the former may call forth the corresponding pro- 

 cesses of the latter, but this is not always necessary. Our sense organs 

 can be influenced without our "noticing" it, that is, without the 

 thinking apparatus being involved. An especially important reaction 

 of the thinking apparatus is memory, that is, the consciousness that 

 an experience which we have just had possesses more or less agreement 

 with former experiences. With reference to the organ of thought, 

 it is the expression of the general physiological fact that every process 

 influences the organ in such a way that it has a different relation to 

 the repetition of this process, from the first time, and moreover that 

 the repetition is rendered easier. This influence decreases with time. 



It is chiefly upon these phenomena that experience rests. Experi- 

 ence results from the fact that all events consist of a complete series of 

 simultaneous and successive components. When a connection between 

 some of those parts has become familiar to us by the repetition of 

 similar occurrences (for instance, the succession of day and night), we 

 do not feel such an occurrence as something completely new, but as 

 something partially familiar, and the single parts or phases of it do 

 not surprise us, but rather we anticipate their coming or expect 

 them. From expectation to prediction is only a short step, and so 

 experience enables us to prophesy the future from the past and pre- 

 sent. 



Now this is also the road to science; for science is nothing but 

 systematized experience, that is, experience reduced to its simplest 

 and clearest forms. Its purposes to predict from a part of a phe- 

 nomenon which is known another part which is not yet known. 

 Here it may be a question of spatial as well as of temporal phenom- 

 ena. Thus the scientific zoologist knows how to "determine," that 

 is, to tell, from the skull of an animal, the nature of the other parts 

 of the animal to which the skull belongs; likewise the astronomer 

 is able to indicate the future situation of a planet from a few obser- 

 vations of its present situation; and the more exact the first obser- 



