152 POPULAR SCIENCE MONTHLY 



garded as unbroken, and are mental phenomena to be looked upon as 

 the invariable concomitants of certain physical changes; or are the 

 two classes of facts to be built into the one series? Those who accept 

 the first alternative are parallelists, and those who accept the second 

 are interactionists. 



Naturally, there is a lively quarrel between the two sects. The 

 parallelist insists that the interactionist has no clear notion of what 

 he means by interaction, when he uses the word ; and he maintains that, 

 did the interactionist realize his position, he would see himself to be 

 little better than a materialist. He has failed to recognize the great 

 distinction between mental phenomena and physical. On the other 

 hand, the interactionist insists that the parallelist, in declaring the 

 series of physical changes to be unbroken, has reduced the mind to a 

 position of utter insignificance. Every action can be accounted for by 

 going back to its physical causes, and to those alone. The mind, then, 

 is a mere decoration; it does nothing; the man is a physical autom- 

 aton, etc., etc. 



I am not going to try to persuade any one, in this paper, to become 

 an adherent of either the one sect or the other. But it does seem 

 rather hard that those who watch the combat should be led to suppose 

 that, with the triumph of the one party, they are condemned to be- 

 come materialists, and, with the triumph of the other, they are turned 

 into automata. It is distressing to be confronted with Scylla and 

 Charybdis, and to see no clear water between. 



What I wish to prove is that the whole matter is one to be re- 

 garded with no other emotion than that of intellectual curiosity; and 

 that it does not matter a particle to the plain man, from the practical 

 point of view, which side wins. 



First let us assume that the interactionist is right. Then ideas and 

 motions in matter may be regarded as belonging to the one series — 

 they are links in the one chain. Now, one can not piece out a defective 

 series of sounds by the insertion of a smell ; one can not, when one tree 

 in an avenue has died, replace it by a tree in a dream. To constitute 

 a series, in any significant sense of the word, things must have some- 

 thing in common; it must mean something to speak of gaps and inser- 

 tions. Let us suppose, for the sake of argument, that it does mean 

 something here, and that ideas are enough like motions in matter to 

 be inserted between certain motions in matter and to form one series 

 with them. 



This may be a form of materialism; but what of that? The man 

 whose day has been full of ideas, of desires and volitions, of plans and 

 purposes, has had just the day that he has had; and the fact that all 

 these are called material or semi-material does not prevent their being 

 just what he has experienced them to be. If some material things can 



