Letters 117.2

We of the Stoic school believe that the Good is corporeal, because the Good is active, and whatever is active is corporeal. That which is good, is helpful. But, in order to be helpful, it must be active; so, if it is active, it is corporeal. They (the Stoics) declare that wisdom is a Good; it therefore follows that one must also call wisdom corporeal.

Seneca, Letters to Lucilius 117.2, translated by Richard Mott Gummere