Full Idea
'Existence precedes essence' means there is no pre-given 'essence' that determines who and what we are. We are self-making beings.
Gist of Idea
Our 'existence' is how we create ourselves, unconstrained by any prior 'essence'
Source
Kevin Aho (Existentialism: an introduction [2014], Pref 'What?)
Book Reference
Aho,Kevin: 'Existentialism: an introduction' [Polity 2014], p.-8
A Reaction
This not a yes/no dilemma. Personally I believe (with Aristotle, and Steven Pinker) that there is a fairly comprehensive 'human nature' which we all share, and is the basis of ethics. On top of that, though, a fair bit of 'self-making' can go on.