European atheism didn’t start clearing its throat until the mid-1600s. At that time, clandestina, or secret manuscripts appeared. Clandestina are anonymous books challenging the existence of God.
Minor nobles and major thinkers of the time started to secretly pass clandestina to each other. Blasphemy was still extremely illegal, and saying God didn’t exist was as blasphemous as you could get.
First came an anthology of clandestine manuscripts that pulled together some of the ancient Greek writings that challenged religious belief. Books with original arguments that added the perspective gained since the Scientific Revolution quickly followed. Then small pamphlets making individual arguments against belief in God and for atheism began appearing across the continent — more than 200 in all.
With the sudden appearance of all of these secret documents, people started (secretly) talking and thinking about the existence of God in ways that were completely unthinkable a few generations earlier and opeing their minds to atheism. They certainly didn’t evict God from Europe’s intellectual life — even the Enlightenment only posted a first eviction notice, maybe turned off a few utilities.
The anonymous clandestine marked the first time early modern Europe seriously considered the possibility that the divine apartment had never been occupied to begin with.