Marsilio Ficino’s Platonic Theology, Volume II

3Nor should we agree with the Epicureans, who suppose that the soul grows together with the body because somewhat larger boys have greater strength than infants, adolescents then excel more each day in strength, and men do likewise until their strength in turn diminishes as the body ages. The relation of soul to limbs is that of an art to its instruments. The art often remains the same and unchanged, though at one time it moves its instruments more easily and at another with greater difficulty, because sometimes they are better fitted for motion and sometimes less fitted. Thus, although the same power always remains in the soul, excessive softness or dryness prevents the limbs from either holding firm or bending equally well. Even the strength which appears to lie in the body depends not so much upon the weight of the flesh as upon the limbs’ natural proportion and skillful formation, both of which pertain more to the vital spirit than to bulk. Nor is the power within the soul acquired by an increase of body—as is plain in those who lie sluggish in idleness, whose bodies grow while their souls make no progress. It is acquired instead through the soul’s own industry—by native ability, practice, and ardor. Who denies that bodily strength is acquired over time? Yet courage is often granted to the soul in a moment, whether reason shows and commands something noble and magnificent or a frenzy supplies the weapons. A small man often overcomes a larger one; and someone who does not grow in body often grows in power of soul. Indeed, while we diminish in body, we often grow in soul. Knowledge and greatness of soul are very often acquired by the soul in an instant.

4A body, however, can neither give nor receive anything except over time. Finally, the soul’s virtue is a certain equality, as the Magi teach, through which the soul accords both with itself and with the true and the good. If by some means a four-angled line were made circular, it would become more perfect—not because it became longer, but because it became more equal. Again, if a lyre were tuned, it would be more perfect, not because it grew larger, but because it became more harmonious. So when a young man matures in virtue, the soul does not grow in quantity; it advances in a certain spiritual equality and harmony.