Montaigne riffing on the vanity of human knowledge is one of the more satisfying themes of his essays. He quotes philosophers, scientists and poets, juxtaposes their beliefs and arguments, and, as often as not, confesses his incapacity for voting a party line, or holding to any line whatsoever. "The writings of the ancients, I mean the good writings, full and solid, tempt me and move me almost wherever they please; the one I am listening to always seems to me the strongest; I find each one right in his turn, although they contradict each other." (Apology for Raymond Sebon).

There's a pronounced conservative streak in Montaigne's skepticism: "Thus when some new doctrine is offered to us, we have great occasion to distrust it, and to consider that before it was produced its opposite was in vogue; and, as it was overthrown by this one, there may arise in the future a third invention that will likewise smash the second." 

Perhaps this is what allows him, despite a memory buzzing with Lucretius and other top-drawer pagan writers, to remain a faithful Catholic in a time of religious upheaval.