Full Idea
The will consists solely in the fact that when something is proposed to us by our intellect either to affirm or deny, we are moved in such a way that we sense we are determined to it by no external force.
Gist of Idea
Our 'will' just consists of the feeling that when we are motivated to do something, there are no external pressures
Source
René Descartes (Meditations [1641], §4.57)
Book Reference
Descartes,René: 'Discourse on Method/The Meditations', ed/tr. Sutcliffe,F.E. [Penguin 1968], p.136