On Two Souls, Against the Manichaeans

⁴ And here, if perchance in their confusion they had inquired of me whether I thought that the soul even of a fly surpasses that light, I should have replied, yes, nor should it have troubled me that the fly is little, but it should have confirmed me that it is alive. For it is inquired, what causes those members so diminutive to grow, what leads so minute a body here and there according to its natural appetite, what moves its feet in numerical order when it is running, what regulates and gives vibration to its wings when flying? This thing whatever it is in so small a creature towers up so prominently to one well considering, that it excels any lightning flashing upon the eyes.