Full Idea
I take 'existence precedes essence' to mean that we do not have a pre-existing self, which organises our behaviour, but rather that we create our self as we go along, through our existence and activities.
Gist of Idea
'Existence precedes essence' means we have no pre-existing self, but create it through existence
Source
report of Jean-Paul Sartre (Existentialism and Humanism [1945]) by Robin Le Poidevin - Interview with Baggini and Stangroom p.222
Book Reference
Baggini,J/Stangroom,J: 'New British Philosophy' [Routledge 2002], p.222
A Reaction
The direct opponent of this is Aristotle, who builds his ethics on a fairly fixed human nature, but even he agrees that we mould our moral characters through our activities, in a circular way. There are not, though, infinite possibilities in mankind.