Elias Finch, a failed mathematician, receives a mysterious book that reveals the differentials—the hidden possibilities and regrets of a life. It leads him to Cora Vane, a woman who became a limit after inverting time's operator. Together, they navigate a manifold of choices, forgiveness, and transformation. Joined by Elias's ex-wife Mira, they learn that change is continuous and love a function, not a constant. The book circulates through generations, a door to becoming. The differential is never zero. The becoming never ends. Ordinary life, with its mint, sunflowers, stones, and small kindnesses, becomes the only proof that matters.
