The quote highlights that even prominent atheists, despite their strong beliefs against the existence of God, may find themselves questioning their stance. Hugo suggests that their intellectual rigor and depth of thought lead them to explore the very essence of belief, blurring the lines of strict atheism. This introspection reflects a profound understanding of existence and the nature of belief. It implies that the pursuit of truth can lead to a form of acknowledgment of a higher power, even if it's not explicitly stated. Their critical thinking and greatness, in fact, serve as a testament to the complexities of belief and doubt. Thus, the quote reveals the intricate relationship between belief, knowledge, and the human experience, emphasizing that questioning one's own beliefs can lead to personal growth and freedom from dogma. Ultimately, the takeaway is that true inquiry into life's mysteries often leads us back to the fundamental questions of existence.