DISCOURSE ON INEQUALITY
Jean-Jacques Rousseau, with a new introduction by Franklin Philip
Oxford University Press, paperback edition (1994)
(first published in 1754)

"...I conceive that there are two kinds of inequality among the human species; one, which I call natural or physical, because it is established by nature, and consists in a difference of age, health, bodily strength, and the qualities of the mind or of the soul: and another, which may be called moral or political inequality, because it depends on a kind of convention, and is established, or at least authorised by the consent of men. This latter consists of the different privileges, which some men enjoy to the prejudice of others; such as that of being more rich, more honoured, more powerful or even in a position to exact obedience.

It is useless to ask what is the source of natural inequality, because that question is answered by the simple definition of the word. Again, it is still more useless to inquire whether there is any essential connection between the two inequalities; for this would be only asking, in other words, whether those who command are necessarily better than those who obey, and if strength of body or of mind, wisdom or virtue are always found in particular individuals, in proportion to their power or wealth: a question fit perhaps to be discussed by slaves in the hearing of their masters, but highly unbecoming to reasonable and free men in search of the truth.

The subject of the present discourse, therefore, is more precisely this. To mark, in the progress of things, the moment at which right took the place of violence and nature became subject to law, and to explain by what sequence of miracles the strong came to submit to serve the weak, and the people to purchase imaginary repose at the expense of real felicity...." Jean-Jacques Rousseau, Discourse on Inequality (1754), Part 1, "A Dissertaion on the Origin and Foundation of the Inequality of Mankind" (quoted from full text on constitution.org)

BOOK DESCRIPTION
A theory of human evolution that prefigured Darwin and made a seminal contribtion to political and social thought, this discourse is the most influential of Rousseau's writings. (Annotation) 

THE READER'S CATALOG–THE NEW YORK REVIEW OF BOOKS
The book that made Rousseau famous, on the happiness of a state of nature and the miseries of civilized sophistication.

Rousseau's sweeping account of humanity's social and political development epitomizes the innovative boldness of the Enlightenment, and it is one of the most provocative and influential works of the eighteenth century.