Chapter 1 begins by questioning why belief in God, once nearly universal and unquestioned in Western society around 1500, had become possible and often prevalent by 2000. It explores the changes that made atheism thinkable and widespread, suggesting that three critical aspects of the earlier world made God’s presence seemingly undeniable: the natural world, society, and an “enchanted” cosmos filled with spirits and moral forces. In this context, atheism was almost inconceivable.

The disappearance of these features alone doesn’t explain the rise of disbelief. This is the argument of the “subtraction” narrative, which claims that belief in God faded as science advanced. Instead, disenchantment and secularization removed traditional supports for belief while creating space for new alternatives, such as exclusive humanism, to emerge.

The shift from a God-saturated world to one where belief is optional involved changing how people experience “fullness,” or a sense of living a meaningful life. In the pre-modern world, fullness came from God, but it could be found in various non-religious sources in the modern secular age. This gradual transformation occurred over several phases, leading to fully developed secular alternatives to religious belief by the late nineteenth century.