The question is in the title:



> 
> Who first claimed the existence / necessity of the empty set ? When did this happen ?
> 
> 
> 


Of course I know that the notation $\emptyset$ goes back to André Weil, and that the first axiom of ZF is that there exists an empty set, but I ask whether this is an older concept.



Historical origin of the empty set
"It can be justifiably argued that Boole had inventented the empty set" [in *The Mathematical Analysis of Logic* (1847)].


[The Empty Set, the Singleton, and the Ordered Pair](https://www.jstor.org/stable/3109881), Akihiro Kanamori (2003).


