The main belief of Enlightenment Thinkers was C: that the use of reason was vital to improving society. Enlightenment thinkers emphasized the importance of rationality, scientific inquiry, and critical thinking as means to understand and transform the world. They sought to challenge traditional authority, superstition, and dogma, advocating for the application of reason and empirical evidence in various aspects of human life, including politics, ethics, and social organization.
While A, B, and D may also have been supported by some Enlightenment thinkers to varying degrees, the overarching emphasis of the Enlightenment was on the power of reason and the potential for human progress through the application of rational thought.