The Enlightenment thinker known for writings on social inequality and human rights is Jean-Jacques Rousseau. In works like "The Social Contract" and "Discourse on the Origin and Basis of Inequality Among Men," Rousseau explored concepts of freedom, equality, and the nature of societal structures. He argued that humans were inherently good but corrupted by society. His ideas were foundational for later human rights philosophies and emphasized the importance of individual liberty and the idea of general will. Rousseau's influential thoughts laid the groundwork for modern political theory and discussions around democracy and civil rights.