LAST EFFORTS OF LOGISTICIANS. i8i 



" But it will be said, How do we demonstrate the 

 existence of this individual ? Is it not necessary that 

 this existence should be established, to enable us to 

 deduce the existence of the class of which it forms 

 part? It is not so. Paradoxical as the assertion 

 may appear, we never demonstrate the existence of 

 an individual. Individuals, from the very fact that 

 they are individuals, are always considered as existing. 

 We have never to declare that an individual exists, 

 absolutely speaking, but only that it exists in a class." 

 M. Couturat finds his own assertion paradoxical, and 

 he will certainly not be alone in so finding it Never- 

 theless it must have some sense, and it means, no 

 doubt, that the existence of an individual alone in 

 the world, of which nothing is asserted, cannot involve 

 contradiction. As long as it is quite alone, it is 

 evident that it cannot interfere with any one. Well, 

 be it so ; we will admit the existence of the individual, 

 " absolutely speaking," but with it we have nothing to 

 do. It still remains to demonstrate the existence 

 of the individual " in a class," and, in order to do 

 this, you will still have to prove that the assertion that 

 such an individual belongs to such a class is neither 

 contradictory in itself nor with the other postulates 

 adopted. 



" Accordingly," M. Couturat continues, " to assert 

 that a definition is not valid unless it is first proved 

 that it is not contradictory, is to impose an arbitrary 

 and improper condition." The claim for the liberty 

 of contradiction could not be stated in more emphatic 

 or haughtier terms. " In any case, the onus probandi 

 rests with those who think these principles are contra- 

 dictory." Postulates are presumed to be compatible. 



