Letters 89.12

The Cyrenaic school abolished the natural as well as the rational department, and were content with the moral side alone; and yet these philosophers also include under another title that which they have rejected. For they divide moral philosophy into five parts: (1) What to avoid and what to seek, (2) The Passions, (3) Actions, (4) Causes, (5) Proofs. Now the causes of things really belong to the “natural” division, the proofs to the “rational.”

Seneca, Letters to Lucilius 89.12, translated by Richard Mott Gummere