TITLE: Historical origin of the empty set
QUESTION [5 upvotes]: 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.

REPLY [13 votes]: "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, Akihiro Kanamori (2003).