LOGIC AND KINDRED SCIENCES. 33 



whereby we introduce reality into the sphere of mind and the peculiar mental 

 modes and forms which affect reality on its being thus made the object of our 

 knowledge. 



20. LOGIC AND PSYCHOLOGY. Psychology is the (speculative) 

 philosophical science which investigates the ultimate causes and 

 principles of life in general, and more especially of conscious and 

 mental life. Embracing all mental activities, it has a wider ma 

 terial object than logic (3, 4). And even where the two sciences 

 partially coincide in the investigation of processes of intellectual 

 thought and reasoning their points of view are quite different. 

 Psychology studies our thought processes as natural phenomena, as 

 natural activities of the living being, with a view to rinding out their 

 genetic principles, and the laws that regulate their production and 

 development. It aims at finding out how men do think, not how 

 they ought to think ; at discovering the natural laws of the actual 

 association and interaction of our thoughts,, not at laying down 

 normative or regulative laws to which ideally accurate thought 

 must conform. The psychologist confines his attention to the 

 subjective or mental conditions of the thought-process ; he is not 

 concerned with the objective reference of the thought-product 

 with its accuracy, its truth, its validity. 



The distinction between the two sciences is, therefore, suffi 

 ciently clear. Yet it is practically impossible to keep them entirely 

 separate. Some psychological knowledge of the nature and func 

 tions of the human mind is indispensable for a proper logical 

 analysis of our fully conscious thought processes. Then, too, this 

 latter analysis is sure to carry us back to purely psychological in 

 quiries concerning the origin of intellectual knowledge and the 

 sentient activities which subserve its acquirement. Hence the 

 many psychological discussions which arise in regard to concep 

 tion, generalization, judgment, induction, etc. Nor, again, is it 

 possible in psychology to treat satisfactorily of the origin and growth 

 of knowledge, without raising questions about its object, its validity \ 

 and the tests of its truth. The psychological analysis and explana 

 tion of our beliefs is hardly separable from the question whether 

 or how far they are logically justifiable. 



Those &quot; critical &quot; questions regarding the objective side of 

 human knowledge questions as to the criteria or tests of its 

 objective truth, arising out of psychology are nowadays usually 

 treated apart (in Criteriology, cf. 17); except in so far as logic 

 claims to derive from an analysis of them certain rules or canons 

 VOL. I. 3 



