There are various and sometimes contradictory ideas about Rousseau's thoughts. Some classify him in the group of enlightenment thinkers and some acknowledge him as an anti-enlightenment philosopher. There is no doubt that Rousseau's thought was affected by some elements of enlightenment, however, he criticized most of its characteristics as well, and challenged rationalism in the age of mastery of reason. The significance of humanity and the freedom of human beings is one of the central concepts in Rousseau's thought, but he considered reason and rationality as a tool for decreasing the very freedom. In Rousseau's view the culture of modernity not only has been constituted due to absence of morality, but also the development of science and art has not improved human's life at all. He believed that only the natural state of human's essence can release him. This paper will explain the enlightenment principles in Rousseau's thought, and compare the affinities and dissimilarities of his beliefs with the other thinkers of the age of enlightenment.