I mean to present my fellow-mortals with a man in all the integrity of nature, and this man shall be myself. (Confessions, Book 1, paragraph 1)

These words most likely mean that Rousseau was writing his

- Schoolwork

- Social Contract

- Letters

- Autobiography

Autobiography.

Explanation:

Rousseau's autobiography, the Confessions, is a unique book, never quite attempted before him, in which the man, Rousseau, speaks about his personal experiences in order to elaborate on most of his influential ideas, like the nature of the State and education. In this curious book, Rousseau also elaborates on some famous passages of a very intimate nature that inspire both a solemn hilarity in the reader and an oddly humane and intricate dimension of this famous thinker.

Autobiography I believe.