Full Idea
To his sense of weakness, man would soon add his needs. Encouraged by indications that their fear was shared, men would soon come together. They would feel the pleasure (and sexual attraction) of their own species. Knowledge then draws them into society.
Gist of Idea
People are drawn into society by needs, shared fears, pleasure, and knowledge
Source
Baron de Montesquieu (The Spirit of the Laws (rev. 1757) [1748], 01.02)
Book Reference
Montesquieu,Baron de: 'Selected Political Writings', ed/tr. Richter,Melvin [Hackett 1990], p.112
A Reaction
He doesn't make the point about 'knowledge' very clear.