The ancient biography as a literary form reflects specific cultural assumptions about what makes a life worth recording and what lessons it should teach. These assumptions differ significantly from modern biographical practice.

Suetonius' Lives of the Twelve Caesars organize each biography around a catalogue of virtues and vices rather than a chronological narrative. The result is vivid character portrayal at the cost of political context. His chapter on Julius Caesar gives us detailed physical description, discussion of his literary output, and extensive cataloguing of his sexual behavior, but requires external sources to understand his political significance.

Plutarch's Parallel Lives pair a Greek with a Roman figure and draw explicit moral comparisons. His stated purpose — moral instruction through the study of great men — reflects a view of history as a repository of examples (exempla) for imitation or avoidance. The Roman rhetorical tradition made heavy use of historical exempla in argumentation, and Plutarch's biographies were partly written to provide a richer supply.

The Lives of the Philosophers tradition — Diogenes Laertius' Lives and Opinions of Eminent Philosophers is the most extensive surviving example — uses biography to transmit philosophical doctrine. The format alternates between biographical anecdote (often apocryphal) and philosophical summary. It reflects a culture in which philosophical tradition was transmitted as much through the character and life example of the master as through the content of the doctrine.