Full Idea
Although one idea can perhaps issue from another, nevertheless no infinite regress is permitted here; eventually some first idea must be reached whose cause is a sort of archetype that contains formally all the reality that is in the idea.
Gist of Idea
One idea leads to another, but there must be an initial idea that contains the reality of all the others
Source
René Descartes (Meditations [1641], §3.42)
Book Reference
Descartes,René: 'Discourse on Method/The Meditations', ed/tr. Sutcliffe,F.E. [Penguin 1968], p.120