512 POPULAR SCIENCE MONTHLY. 



free use of the conception of consciousness as a co-ordination of 

 forces capable of occasional disruption, although he seems to have 

 been led to that notion by the Herbartian psychology. Professors 

 Janet and Binet also teach analogous doctrines without reference 

 to the brain processes, and Prof. William James seems at times to 

 hold a similar position. 



In sharp antithesis to the theory of dependence stands the 

 theory of independence. According to this doctrine, mind and 

 matter are essentially distinct in nature, and are capable of inde- 

 pendent existence, although in fact sometimes closely related. 

 Many mental states, as sensations, are caused by physical processes, 

 and, vice versa, many physical processes, as some bodily move- 

 ments, are caused by mental states; but this relation of action 

 and interaction is purely accidental, and can be dissolved without 

 the destruction of either mind or matter. This theory has been 

 stated in many forms, and is involved more or less implicitly in 

 many philosophies. In one form or another it has been the domi- 

 nant theory in every epoch of human thought, it lies at the foun- 

 dation of most religions, and is to-day accepted by the mass of 

 men ; yet in the scientific world it has fallen into such disfavor 

 that in many circles it is almost as disgraceful to avow belief in 

 it as in witchcraft or ghosts. 



The chief argument usually alleged in justification of this at- 

 titude is that the theory of independence violates the law of con- 

 servation of energy, which is justly regarded as one of the great- 

 est scientific generalizations of this century. That law requires 

 that in all the manifold flux of physical phenomena certain defi- 

 nite and quantitative relations should exist between the amount 

 of work done and the amount of energy expended, thus binding all 

 physical processes into a closed series. To admit mental phenom- 

 ena into that series as a mode into which physical energy might 

 be transformed would, it is claimed, break the law first, because 

 the new elements are non-physical, and it is inconceivable that 

 the non-physical should affect the physical ; and, second, because 

 mental states can not be measured, and therefore can not consti- 

 tute an equivalent of anything. 



This a 'priori objection does not seem to me to possess much 

 force. The argument from inconceivability has been urged 

 against every new conception introduced into science ; it was 

 never more weighty then when hurled against the bold specula- 

 tors who claimed that the earth was round and that the antip- 

 odes nevertheless did not fall off. That a thought should cause 

 the disintegration of a molecule is intrinsically neither more nor 

 less inconceivable than that a disturbance in an imponderable 

 entity like ether should shatter an oak tree. What is inconceiv- 

 able to one generation becomes the commonplace of the next. 



