Full Idea
Epicurus alone saw that gods must exist because nature herself has imprinted an idea of them in the minds of all mankind.
Gist of Idea
Epicurus saw that gods must exist, because nature has imprinted them on human minds
Source
report of Epicurus (fragments/reports [c.289 BCE]) by M. Tullius Cicero - On the Nature of the Gods ('De natura deorum') I.43
Book Reference
Cicero: 'The Nature of the Gods', ed/tr. McGregor,Horace [Penguin 1972], p.87