Full Idea
It is absolutely necessary that everything in the world be either a being or a mode [manière] of a being.
Gist of Idea
Everything that exists is either a being, or some mode of a being
Source
Nicolas Malebranche (The Search After Truth [1675], III.2.8.ii), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 13.4
Book Reference
Pasnau,Robert: 'Metaphysical Themes 1274-1671' [OUP 2011], p.260