316 Heredity. 



how the transition was brought about from the physiological to 

 the psychological epoch from the period of no thought to the 

 period of thought. The development school, however, is bound 

 to maintain this ascending evolution. This was perceived even 

 by Lamarck, and he boldly supposes the existence of a primitive 

 race of non-sentient animals. ' In producing life,' says he, ' nature 

 did not abruptly set up so high a faculty as that of sense. Nature 

 did not possess the means of creating this faculty in the imperfect 

 animals belonging to the earliest classes of the animal kingdom.' x 

 When we consider from the biological point of view the pheno- 

 mena of mental activity, and compare them with purely vital 

 facts, we find that both possess in common this essential point, 

 that they are a correspondence. Herbert Spencer has shown how 

 physiological life consists of a correspondence between a being 

 and its environment, 2 and how in the sum of actions and reactions 

 which constitute life there is a continual adjustment of internal to 

 external relations, so that the degree of life varies as the degree of 

 correspondence, perfect life being perfect correspondence. But 

 mental life is, like bodily life, a correspondence. To think, or to 

 have a cognition, is to have in our mind a certain state corres- 

 ponding to a certain state without ; and this correspondence also 

 is found in all possible degrees, from the zoophyte to man, so that 

 the degree of cognition is measured by the degree of correspond- 

 ence. Between life and thought, therefore, there are other 

 differences than that between a partial and a total correspondence, 

 between a correspondence imperfectly unified (life) and a corres- 

 pondence perfectly unified (consciousness) ; finally, and here is the 

 mystery, between an unconscious and a conscious correspondence. 

 If we could know how the simultaneous becomes successive, and 

 how plurality becomes unity, then we could tell how thought 

 results from life. 3 They suppose that they have explained this 



1 Philosophic Zoologique, Discours Preliminaire, 7. 



2 Principles of Biology. For instance, there must be in a plant certain 

 changes answering to the changes of its environment (humidity, dryness, etc.). 



3 An author who holds the genesis of the forms of thought through evolution 

 has developed the singular hypothesis that it is possible to ' think in space. ' 

 (Murphy, Habit and Intelligence, ch. xxxvii.) For this, says he, it would suffice 

 that a mind, in place of thinking as our mind does, with words succeeding one 



