The central theme expressed in the writings of Enlightenment thinkers was a belief in reason and the potential for human progress. Philosophers like John Locke and Jean-Jacques Rousseau emphasized the importance of liberty, equality, and the social contract as a basis for governance. They argued that individuals have the capacity to reason and make rational choices, which leads to the development of just societies. Enlightenment thought encouraged questioning authority and traditional hierarchies, promoting ideas that would later shape democracy and human rights movements across the globe.