The influential philosopher who wrote "The Social Contract" is Jean-Jacques Rousseau. His work emphasizes the concept of popular sovereignty and the idea that legitimate political authority arises from a social contract agreed upon by the governed. Rousseau's ideas challenged existing political theories and influenced democratic thinking, asserting the importance of individual freedom and collective governance. His philosophy laid the groundwork for modern political thought and inspired revolutions, advocating for equality and the notion that the general will should guide societal progress.