This paper gives a new account of Roman birthday-cult and the genius in the works of Horace. Horace’s implicit theology of genius, it argues, related the public sphere of the nascent State (itself buttressed by birthday cult) to the private sphere of his relationship to Maecenas, and to the solitary sphere of his relationship to himself. At its core, this paper solves two problems raised by his final birthday-poem, Odes IV,11, “The Blood-Offering Problem” and “The Birthday Problem”. In revealing Horace’s identification of his births and rebirths with those of Maecenas, this paper reveals Horace’s novel coordination of cosmos, imperium and the individual, in ways that clarify his poetry, his new political theology of empire, and the history ...