[Sethomas]

Sartre summarizes Existentialism by stating that "existence precedes essence" (unfortunately my edition for class was a [shitty] translation, so I can't comment on his semantics), but I've not read L'être et le Néant yet. What I've encountered him saying that in was a collection of his speeches on Existentialism, namely Part 4: Existentialism as a Humanism. I wouldn't be flabbergasted if he said that a dozen other places, but that's the only one I know for sure.