How does Rousseau challenge the idea of human beings as essentially rational or of human psychology as ruled by intellect?

In his essay,
"What is the origin of inequality among men and is it authorized by the natural law?",
Rousseau applied his view of the development of individuals to the development of society
itself. It was entered in a competition held by the Dijon Academy of Arts and Sciences in 1754.
Four years earlier he had won the competition with another essay but this one, though more
popular in years to come, won no award.

Rousseau's position on
the...