Why did ancient Greek religion have no sacred book or official creed?

Ancient Greek religion did not rely on a sacred book or an official creed because it was not based on a codified body of dogma or enforced orthodoxy. Instead, the religion centered on the belief that gods existed and the practical requirement to perform ritual and sacrifice to ensure the gods received their due.12

Because there was no attempt to enforce a specific set of beliefs, the concept of an official creed was essentially incomprehensible to the Greeks. While various sacred writings existed—such as Homeric Hymns, oracles, and funerary inscriptions—these were not liturgical texts or doctrinal foundations. Priests functioned primarily as caretakers of cults rather than as a clergy responsible for maintaining religious dogma. The religious worldview was instead embodied through a large corpus of Greek mythology, which remained flexible and subject to change by writers and poets over time.12