Preface 



with all the external signs of pain, just as if it were 

 suffering. When an earthworm is cut in two both 

 pieces move convulsively. Are we to say that both are 

 suffering, or what appears to me much more rational, 

 rather to think that the traumatism 1 has set up a 

 violent reflex action ? ' 



Therefore if we attribute sensibility to animals low 

 in the scale, it is by a descending induction. Our 

 reasoning goes from the summit to the base. 



Let us proceed inversely : if, setting aside our own 

 personal experience, we consider the very inferior animals, 

 we shall be logically obliged to deny them sensibility, 

 since all their reactions can be explained by reflexes. 

 Sensibility to pleasure or pain is for them an unnecessary 

 hypothesis, and conformably to the principle of method- 

 ology known as economy of hypothesis, it should be 

 put aside. 



But then, why admit this sensibility in the highest 

 animals ? Here also everything can be explained by 

 reflexes. As Richet observes, the yelp of a beaten dog, 

 may, strictly speaking, be only a reflex movement ! 

 And this reasoning is not absurd, since it is Cartesian. 

 Nevertheless, pushed to the negation of human sensi- 

 bility it becomes untenable. It impels us to place man, 

 as did Descartes, outside animal life; which is evidently 

 a gross and dangerous mistake. 



Thus the method which consists in starting from 

 the base in order to explain one of the essential vital 

 principles is convicted of flagrant error. It is therefore 

 under suspicion for all the rest. No doubt it will be 

 objected that the contrary method may also lead us 

 astray: as, for instance, says Le Dantec, 2 'the famous 

 observation of Carter, in which an amoeba lay in wait 

 for a young Acineta about to detach itself from the 



1 Traumatism the state of being wounded. 

 ! Le Dantec : Le Dtterminisme Biologique. 



XV 



