618 THE POPULAR SCIENCE MONTHLY. 



my friend's bodily structure. Now, the difference between the ma- 

 terialist and the positivist lies just in this, that the former is embar- 

 rassed at the decided effects which he sees produced by impalpable 

 things, while the latter escapes such embarrassment entirely, simply 

 by not having set up any arbitrary standard of what constitutes reality. 

 The materialist does not want to recognize anything as real that does 

 not more or less resemble his piece of granite, that does not affect the 

 tactual sense ; while the positivist is content to recognize all things as 

 real that reveal their existence to the mind by affecting it in a definite 

 manner. He cordially admits that the piece of granite does this, but 

 he says also that a thousand things that have no analogy with it what- 

 ever do it as well. 



Some people, chiefly materialists, will heedlessly say that this is 

 idealism. But they are totally mistaken. Idealism consists in affirm- 

 ing reality of the mind and denying it to objective existences, or in 

 affirming that the apparent distinction between subject and object is 

 unreal and illusive. The positivist does neither the one nor the other. 

 He simply abstains from setting up an arbitrary standard of reality. 

 He talks neither of mind-stuff nor of world-stuff ; such talk, indeed, 

 he can not help regarding as all stuff. He knows that he knows and 

 that he feels, and that there are certain definite sources of knowledge 

 and feeling. He perceives that he has an environment upon which he 

 can act, and which reacts upon him. That environment is a very com- 

 plex one, answering to the complexity of his own nature. There is 

 nothing within him, indeed, that has not some answering element 

 without. Regarding him first as an animal, he has a nutritive sys- 

 tem, which has its answering external realities ; he has a nervous and 

 muscular system, to which the outward frame of things in like manner 

 responds. Taking a higher point of view, he has intellectual faculties 

 which lay hold of the relations of things in the outer world ; he has 

 an emotional nature, with moods that vary according to the nature of 

 the stimulus they receive ; he has social faculties and propensities that 

 find exercise in the domain of society ; he has powers of moral judg- 

 ment that recognize, apart altogether from the verdict of society, the 

 essential moral qualities of actions. To each range or level of function 

 in the individual man there are corresponding realities in the outer 

 world ; and it is to be observed that what are realities to one set of 

 functions are not realities in the same sense to any other. The nutri- 

 tive quality of an apple is not a reality to the muscular sense, nor is 

 the weight of the apple which is cognized by the muscular sense a 

 reality to the nutritive function. The test of reality is, we thus see, 

 the existence or non-existence of definite relationship. To illustrate 

 the same form further, we may observe that the physical properties of 

 bodies are not realities to the intellectual faculty that investigates 

 their spatial or numerical relations. The weight of a statue, or the 

 chemical composition of the marble or bronze of which it is made, is 



