Alexander III was the son of Philip II of Macedon and Olympias; in boyhood a pupil of Aristotle. Succeeding to the throne in 336 BCE, in not quite thirteen years he conquered the Persian Empire, reached India, founded a number of cities (above all Alexandria in Egypt), and created a dominion of unheard-of extent. He died at Babylon in 323 BCE, aged thirty-two, of a fever (the cause is also debated — drink, or poison). The empire fragmented at once in the wars of the Diadochi.

Alexander appears in Marcus not as a philosopher but as a historical exemplum: the greatest of conquerors, whose power and fame did not annul death. He is a figure for the memory of death, not a source of doctrine.