Mythological beliefs among the ancient Greeks persisted into the classical age. The Greeks believed that after death the psyche, or vital essence of a person, lived on in the underworld. The Greek writer Homer (circa 800–700 BCE) greatly influenced classical Greek attitudes about death through his epic poems the Iliad and the Odyssey. Greek mythology was freely interpreted by writers after Homer, and belief in eternal judgment and retribution continued to evolve throughout this period.

Certain Greek philosophers also influenced people's outlook about death. Pythagoras (circa 580–500 BCE), for example, advocated Orphic teachings about the cycle of birth and death. He opposed euthanasia ("good death," or mercy killing) because it disturbed the soul's journey toward final purification as planned by the gods. On the other hand, Socrates (circa 470–399 BCE) and Plato (circa 428–347 BCE) believed that people could choose to end their lives if they were no longer useful to themselves or the state.

Like Socrates and Plato, the classical Romans (circa 509–264 BCE) believed that a person suffering from intolerable pain or an incurable illness should have the right to choose a "good death." Classical Greeks and Romans considered euthanasia a "mode of dying" that allowed a person's right to take control of an intolerable situation. They distinguished it from suicide, an act considered to be a shirking of responsibilities to one's family and to humankind.