What argument did Jean-Jacques Rousseau make in A Discourse on the Sciences and the Arts?

In his prize-winning essay A Discourse on the Sciences and the Arts (1750), also known as the First Discourse, Jean-Jacques Rousseau argued that the history of human life has been a history of decay.12

Responding to a question posed by the Academy of Dijon regarding whether the restoration of the sciences and arts had tended to purify morals, Rousseau contended that modern progress had corrupted, rather than improved, humanity. He posited that while people are good by nature, they have been corrupted by society and civilization. Rousseau did not suggest that society is inherently evil, but rather that it has taken a wrong direction, becoming more harmful as it has grown more sophisticated. This central theme—that human beings are naturally pure but have been corrupted by the development of society—became the cornerstone of his philosophical work throughout his life.12