2^2 Tiii; ki:lati()>; of jjody and mind. 



and Ijiuly are equally real and reciprocally act upon and inriiicnce 

 each other. 



To nie it seems fairly clear that we must lutld some theory 

 of interaction — that the mind does in some \va_\- control and set 

 in motion processes of the nerve-system, and that the body 

 intiuences the mind in materialising its thoughts or making them 

 symbolical in character. But as the theory of interaction is 

 usually stated, it seems oi)en to very serious objections. The 

 brain is presented to us first as an independent svstem. actuated 

 exclusively b\- mechanical laws of natural causation, and then, 

 "because such a system so actuated cannot explain ])sychical facts, 

 another inde])endent principle, called the soul or mind, is ])rought 

 in and is rej^resented as influencing and controlling a system 

 which, we were just before assured, was a swstem operating 

 exclusively by mechanical laws. I think Clifford speaks some- 

 where of a train, in wdiich the luggage van is connected with 

 the rest of the coaches bv the feelings of friendsbip l)el\\eLn the 

 guard and the engine-driver. 



Ilow^ can a system governed by mechanical and chemical 

 laws and w^orking by natural causation tind room for the mind 

 with its implications of freedom and pur])Ose and intelligent 

 choice? Does not the theor\- of interaction simply try ti> mix 

 up things which are mutually incom]\'itible ? According to it 

 body becomes a mechanical system which fails to act by 

 mechanical law (so far as an influence of mind is admitted ). and 

 mind becomes a s])iritual system which does not act spiritually, 

 but mixes itself up in mechanical processes. Both systems fail 

 to be true to their own special and characteristic i)rinciples. 



It is difficult to understand whether mind interferes occa- 

 sionalh' with a ])rocess which is normalK' mechanical, or whether 

 it is essentiallv mixed u]) in these processes; and equally diffi- 

 cult to understand how either one or the other is possible. In 

 order to illustrate what seems to me the way out of the difhculty, 

 let us consider the case of an ordinary machine. Here pur- 

 posive contrivance and dead mechanical action are both ])resent. 

 Each part of the machine has its ])urpose in connection with the 

 whole, and the whole again has its purpose in connection Avith 

 the needs or comforts of human life. But this puri)()sive ele- 

 ment is im])orted from within. It was located in the mind of 

 the engineer who made the machine; the machine itself knows 

 nothing of such jiurpose ; no cog or ])iston or wheel recognises 

 anv community of interest with the others, but all work in blind 

 obedience to mechanical law and in .absolute inditi'erencL- h> any 

 useful result that may ensue. 



But let us imagine a machine which is itself active and pur- 

 posive, instead of having its i)ur])Ose im])arted to it from withmit; 

 and we shall have a i)icture of the interaction that we want. 

 The influence of the life and the mechanism will be recii)rocal. 

 On the one hand the i)ur])osive life will only be able to manifest 

 itself under material conditions; will have to grind itself out 



