Although the narrator begins The Unbearable Lightness of Being with a discussion of eternal return, he uses that idea to introduce a thought experiment that will underpin the thematic structure of his narrative: the dichotomy between lightness and weight. The idea of eternal return gives weight to events and decisions: Every individual choice must be made with great care, since it is bound to be repeated for all eternity. The narrator terms eternal return a “mad myth,” suggesting that the novel will be at the very least an interrogation of this myth, if not an outright refutation. Nietzsche called the possibility of eternal return the “greatest burden” and the narrator takes issue with the notion that meaning comes from weight. He is drawn to the idea that human lifetimes are rendered light by their transience, that what ultimately characterizes existence is not the infinite but the finite: An individual is born, lives, and dies but once. And yet, the narrator cannot help but be struck by the sheer number of metaphors that associate weight and heaviness with meaning, value, and depth. The narrator also brings up Greek philosopher Parmenides in this initial discussion, pointing out that Parmenides conceived of the world as a series of opposing pairs, and that in his estimation, weight was negative and light positive.