124 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



association is that there is some dependence of one event 

 on the other. When the association is of a very close spatial 

 or temporal kind, there is almost always conceived a new 

 event which is the associative union of the two; in this 

 respect the correlation of events is the opposite of their 

 isolation, discussed earlier in the chapter. When the as- 

 sociation of the two events is infrequent, the dependence 

 of the one upon the other is slight; when it occurs often 

 the dependence is more pronounced; when it occurs univer- 

 sally the dependence is absolute. Correlation is the mental 

 operation by which one symbolizes the fact of connections 

 in nature, and symbols for such correlations, when they occur 

 repeatedly, are called scientific laws. If one should note 

 that two or three of his acquaintances who have red hair 

 are quick tempered, he might be led to believe that the 

 properties are related, though he would attach slight prob- 

 ability to it; if he found it to be illustrated in a much more 

 extended group he would begin to suspect a connection; if 

 he found it to be true universally he would be obliged to 

 express it in a universal law. (The problem has, of course, 

 been enormously simplified for purposes of illustration.) 

 There is reason to believe that the correlations which occur 

 in descriptive science, i.e., where one is concerned only with 

 the most obvious features of nature, are not universal. 

 That events are universally connected in nature is not one 

 of its apparent features, but discernible only through elab- 

 orate exploratory devices. Hence correlations at this stage 

 of study are primarily statements of frequencies. 



The third factor in the control of the state of mind is 

 unconscious inference. Here, again, there is some doubt 

 as to whether this should be called a disturbing factor since 

 it may be present in all observation. But that it is a very 

 common source of error cannot be doubted. One reads into 

 situations and supposes to be actually present elements 

 which are the results of unconscious inference. A snow 

 scene looks cold, and velvet looks soft; a table-top which 

 is observed as a parallelogram is assumed to be rectangular; 



