We seek to know only because we desire to find enjoyment; and it is impossible to conceive why someon who had neither desires nor fears would go to the bother reasoning.
Gist of Idea
No one would bother to reason, and try to know things, without a desire for enjoyment
Jean-Jacques Rousseau (Discourse on the Origin of Inequality , Part I)
This appears to be an echo of Hume's pessimism about the autonomy of reason. This downgrading of reason is a striking feature of the Enlightenment, which presumably culminates in the romantic movement.
Rousseau,Jean-Jacques: 'The Basic Political Writings', ed/tr. Cress,Donald A. [Hackett 1987], p.46
Idea 3807 Reason is and ought to be the slave of the passions [Hume]