Robert Wokler, Rousseau: A Very Short Introduction (Oxford University Press, 2001).

From the publisher:

In this study of Rousseau’s life and works, Robert Wolker shows how his philosophy of history, his theories of music and politics, his fiction, educational, and religious writings, and even his botany, were all inspired by revolutionary ideals of mankind’s self-realization in a condition of unfettered freedom. He explains how, in regressing to classical republicanism, ancient mythology, direct communication with God, and solitude, Rousseau anticipated some post-modernist rejections of the Enlightenment as well.

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