200 MYSTICISM AND LOGIC 



a given state of mind always corresponds, and vice versa, 

 i.e. that there is a one-one relation between them, so that 

 each is a function of the other. We may also assume, 

 what is practically certain, that to a given state of a 

 certain brain a given state of the whole material universe 

 corresponds, since it is highly improbable that a given 

 brain is ever twice in exactly the same state. Hence 

 there will be a one-one relation between the state of a 

 given person's mind and the state of the whole material 

 universe. It follows that, if n states of the material 

 universe are determinants of the material universe, then 

 n states of a given man's mind are determinants of the 

 whole material and mental universe assuming, that is 

 to say, that psycho-physical parallelism is true. 



The above illustration is important in connection with 

 a certain confusion which seems to have beset those who 

 have philosophised on the relation of mind and matter 

 It is often thought that, if the state of the mind is deter- 

 minate when the state of the brain is given, and if the 

 material world forms a deterministic system, then mind 

 is " subject " to matter in some sense in which matter is 

 not " subject " to mind. But if the state of the brain is 

 also determinate when the state of the mind is given, it 

 must be exactly as true to regard matter as subject to 

 mind as it would be to regard mind as subject to matter. 

 We could, theoretically, work out the history of mind 

 without ever mentioning matter, and then, at the end, 

 deduce that matter must meanwhile have gone through 

 the corresponding history. It is true that if the relation 

 of brain to mind were many-one, not one-one, there would 

 be a one-sided dependence of mind on brain, while con- 

 versely, if the relation were one-many, as Bergson sup- 

 poses, there would be a one-sided dependence of brain on 

 mind. But the dependence involved is, in any case, only 



