Letters 113.2

The soul, men are agreed, is a living thing, because of itself it can make us living things, and because “living things" have derived their name therefrom. But virtue is nothing else than a soul in a certain condition; therefore it is a living thing. Again, virtue is active, and no action can take place without impulse. And if a thing has impulse, it must be a living thing; for none except a living thing possesses impulse.

Seneca, Letters to Lucilius 113.2, translated by Richard Mott Gummere