Letters 31.8

And besides this, in order that virtue may be perfect, there should be an even temperament and a scheme of life that is consistent with itself throughout; and this result cannot be attained without knowledge of things, and without the art which enables us to understand things human and things divine. That is the greatest good. If you seize this good, you begin to be the associate of the gods, and not their suppliant.

Seneca, Letters to Lucilius 31.8, translated by Richard Mott Gummere