Full Idea
Desire is man's very essence, insofar as it is agreed to be determined, from any affection of it, to do something. ...Desire is appetite, together with the consciousness of it.
Gist of Idea
Whenever we act, then desire is our very essence
Source
Baruch de Spinoza (The Ethics [1675], III Def of Aff I)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. Curley,Edwin [Penguin 1996], p.104
A Reaction
[I think that is the gist of it!] This sounds a bit circular, but seems to say that actions are almost entireoy the expression of desires.