which means: zero is the number of things satisfying a condition never satisfied.
But as never means in no case I do not see that the progress is great.
I hasten to add that the definition M. Couturat gives of the number 1 is more satisfactory.
One, says he in substance, is the number of elements in a class in which any two elements are identical.
It is more satisfactory, I have said, in this sense that to define 1, he does not use the word one; in compensation, he uses the word two. But I fear, if asked what is two, M. Couturat would have to use the word one.
VIII
But to return to the memoir of Burali-Forti; I have said his conclusions are in direct opposition to those of Cantor. Now, one day M. Hadamard came to see me and the talk fell upon this antinomy.
"Burali-Forti's reasoning," I said, "does it not seem to you irreproachable?" "No, and on the contrary I find nothing to object to in that of Cantor. Besides, Burali-Forti had no right to speak of the aggregate of all the ordinal numbers."
"Pardon, he had the right, since he could always put