Full Idea
If a number of individuals so unite in one action that they are all simultaneously the cause of one effect, I consider them all, so far, as one individual thing.
Gist of Idea
A thing is unified if its parts produce a single effect
Source
Baruch de Spinoza (The Ethics [1675], II Def 7)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. White,WH/Stirling,AH [Wordsworth 2001], p.46
A Reaction
Interesting. If a mob burn down a town, is that one effect, making the mob one thing? If a ball breaks a window, is that one effect, or a multitude of knock-on effects? Spinoza's view is very coarse-grained.