Jean-Jacques Rousseau

As long as we continue to study and cite Hobbes, Rousseau, and Marx—none of whose views of human nature can today be ranked as scientific—it would be perversely backward-looking to refuse even to consider sociobiology and what follows from it.

Peter Singer, Ethics and sociobiology, Philosophy & public affairs, vol. 11, no. 1, 1982, pp. 40–64, pp. 40-64

[Kant] said that he had to read Rousseau’s books several times, because, at a first reading, the beauty of the style prevented him from noticing the matter.

Bertrand Russell, A history of western philosophy: and its connection with political and social circumstances from the earliest times to the present day, London, 1946, p. 731