Letters 89.16

The natural side of philosophy is twofold: bodily and non-bodily. Each is divided into its own grades of importance, so to speak. The topic concerning bodies deals, first, with these two grades: the creative and the created; and the created things are the elements. Now this very topic of the elements, as some writers hold, is integral; as others hold, it is divided into matter, the cause which moves all things, and the elements.

Seneca, Letters to Lucilius 89.16, translated by Richard Mott Gummere