258 Heredity. 



show more and more conclusively that this correlation is as com- 

 plete as possible ; that it is constant ; that it is to be seen even in 

 the most insignificant cases, and that it admits of no exception. 

 It is of great importance for us to establish this truth here : for if 

 we could succeed in showing it to be highly probable as yet we 

 cannot hope for certainty that every psychological state supposes 

 a physiological antecedent, a considerable advance would have 

 been made in our inquiry into the causes. In the order of pheno- 

 mena, all our science consists in demonstrating permanent co- 

 existences and permanent successions. Suppose this permanent 

 co-existence of a physiological and a psychological state estab- 

 lished, we can then go further, and draw the deduction that in 

 every individual an habitual mental state must answer to an 

 habitual nervous state. The mental constitution of a poet and 

 that of a mathematician imply each a physiological organization 

 differing from the other in certain points. We can go further, and 

 extend to the species what has just been said of the individual. 

 The permanence of a certain turn of mind in a family during 

 several generations supposes the permanence of certain correspond- 

 ing physiological characters during the same number of genera- 

 tions. This leads us in the direction of the required answer, for 

 to resolve a problem is to translate a proposition which implicitly 

 contains a truth into another which gives a glimpse of it, and 

 this in turn into another which exhibits it clearly. 



For the present, let it suffice to establish our premisses. Evi- 

 dently experience only can decide whether every psychological 

 state is connected with a physiological state ; this is a question 

 of fact rather than of theory. Still, we cannot enumerate all pos- 

 sible cases ; we cannot take all the states of consciousness in 

 succession and show that they correspond, each with a particular 

 nervous state. Such a demonstration would be endless, and it 

 would, moreover, be in many cases impossible. We must, then, in 

 accordance with Bacon's precept, confine ourselves to a few 

 selected, striking, decisive facts, to expcrimcnta lucifera which may 

 serve as a basis for a sound induction. We will, then, show from 

 examples that sentiments and ideas are referable to certain states 

 of the organs, though at first sight they would seem to be entirely 

 independent of them. 



