Full Idea
Existentialism says that existence comes before essence - or, if you will, that we must begin from the subjective.
Gist of Idea
Existence before essence (or begin with the subjective)
Source
Jean-Paul Sartre (Existentialism and Humanism [1945], p.26)
Book Reference
Sartre,Jean-Paul: 'Existentialism and Humanism', ed/tr. Mairet,Philip [Methuen 1980], p.26