Full Idea
The concept of forces or powers ..for whose explanation I have set up a distinct science of dynamics, brings the strongest light to bear upon our understanding of the true concept of substance.
Gist of Idea
The concept of forces or powers best reveals the true concept of substance
Source
Gottfried Leibniz (De primae philosophiae emendatione [1694], G IV 469), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 4
Book Reference
Garber,Daniel: 'Leibniz: Body, Substance, Monad' [OUP 2009], p.128
A Reaction
My own experience was that as soon as I encountered the notion of a 'power' in the metaphysics of science (see Molnar on this) the whole thing began to form a coherent picture. Powers rule.