Jonathan Miller, the physician-turned-broadcaster known for Beyond the Fringe, sets out to trace where his own unbelief comes from and finds it has a long, tangled history. He starts with the classical skeptics and the Epicureans, moves through Spinoza's excommunication and Hume's quiet subversions, and lands in the twentieth century with the scientific challenges to religious authority that followed Darwin. Along the way he sits down with thinkers including Daniel Dennett, Colin McGinn, and Steven Weinberg, letting them argue for reason and doubt as intellectual traditions in their own right rather than mere absence of faith. Miller treats the September 11 attacks and the harder political edge they gave to Western monotheism as a hinge point, using it to ask why disbelief still carries social risk even in supposedly secular societies. Shot as a personal essay as much as a history lesson, with Miller narrating in his own unmistakably digressive style, the film treats atheism as a position with a genealogy, not a modern invention.