Full Idea
Confused notions called 'universal', such as 'man', have arisen because so many images of individual men are formed that they exceed the power of imagination, ...so it imagines that only in which all of them agree, ...expressed by the name 'man'.
Gist of Idea
The 'universal' term 'man' is just imagining whatever is the same in a multitude of men
Source
Baruch de Spinoza (The Ethics [1675], II Pr 40)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. White,WH/Stirling,AH [Wordsworth 2001], p.79
A Reaction
[very compressed] This strikes me as correct. I don't see how you can discuss universals without bringing in the way in which human psychology operates.