It's worth keeping in mind that the age of the enlightenment coexisted with the age of colonialism. Indeed, consider how much the founding fathers and the framers of the Constitution were influenced by Enlightenment era thinkers: there is a common thread tying these two subjects together.
In any respect, I would suggest one topic of critical importance is religion. Religion was an immensely powerful force throughout the Early Modern Era (especially in the aftermath of the Reformation), and a significant subject of debate within the Enlightenment. When reading writers such as Diderot or Voltaire, you can observe a critique of organized, traditional religion as well as of the abuses of power and corruption that could be found within it. Moreover, however, the enlightenment contained criticisms that cut to the heart of Christian theology itself, and many enlightenment era thinkers turned towards the more impersonal God envisioned by deism instead.
Meanwhile, religion was key from the very...
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