118 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



the physiological medium, nevertheless one can easily con- 

 vince himself of the existence of certain factors which may 

 be lumped under the term "state of mind" having a poten- 

 tially disturbing influence. His problem is either to elim- 

 inate these elements or to ascertain the character of the 

 modification which is due to them. What must be assured 

 is that there is no error in the location of the appearances 

 of the object in their proper contexts. 



The first of these factors is the selective activity of atten- 

 tion. This can hardly be called a disturbing factor, since 

 only by means of it can one become clearly aware of any- 

 thing. Furthermore, it is not an abnormality in the sense 

 that it would be absent from normal observation. What 

 should be emphasized with reference to it is simply that it 

 determines isolated systems in much the same sort of way 

 that physical operations do. The isolation, however, is 

 not one which eliminates or counteracts environmental in- 

 fluences, as is the case with physical operations, but rather 

 one which neglects. The observer pays no attention to the 

 associated factors, and thus considers them as non-existent. 

 When there is a conscious recognition of this act of neglect, 

 the selective act of attention cannot be called disturbing. 

 But attention is often unconsciously selective. Frequently 

 one neglects environmental factors without being aware 

 that he is doing so. For example, one easily overlooks mis- 

 spelled words even when he is reading proof. It is a common 

 experience that one observes in any situation what he expects 

 to observe and fails completely to note other elements, 

 even when they are of great intensity. Hence the selectivity 

 of attention must be admitted as a potential source of error. 



Second, and most important among the factors in the 

 control of the state of mind, are those associated with 

 symbolizing the data. As was indicated in Chapter III, 

 knowing is not merely acquaintance but description as well. 

 Science must not only get its data; it must endeavor to 

 portray them by various symbolic devices. Events are 

 private and transitory as they enter into awareness, and if 



