Full Idea
Cohen's method of 'forcing' produces a new model of ZFC from an old model by appending a carefully chosen 'generic' set.
Gist of Idea
'Forcing' can produce new models of ZFC from old models
Source
Penelope Maddy (Naturalism in Mathematics [1997], I.4)
Book Reference
Maddy,Penelope: 'Naturalism in Mathematics' [OUP 2000], p.66