The theme of corruption is closely related to that of nature. Corruption is what Rousseau feels he has to strip away to get to the real nature of man. Corruption is also an important part of the process of human development that he describes. At the same time that human reason develops, and enlightenment emerges, man is corrupted and undergoes a decline from his original condition. Rousseau is clear that this corruption is both a mental and a political process. Mental corruption occurs as man becomes subject to a new system of needs and to the operation of amour propre. His corruption is evident in the attention he now pays to the opinion of others, his loss of basic pity for other creatures, and his general dissatisfaction with life. As Rousseau puts it in Part Two of Discourse on Inequality, modern man has "nothing more than a deceiving and frivolous exterior, honor without virtue, reason without wisdom, and pleasure without happiness."

Corruption is also a political phenomenon, however. Rousseau's description of modern society shows that it is based upon a trick played on the poor, and that it compares unfavorably with both the state of nature and with early society. Political society is corrupt because it is based on a lie, which is used to exploit those who believed that it would protect their freedom. Ultimately both kinds of corruption reinforce each other.