“According to that,” you say, “you are under no obligation to the sun or to the moon; for they do not perform their movements solely because of you.” But, since the purpose of their movements is to preserve the cosmos, they perform their movements for my sake also; for I am a part of the cosmos. And besides, our position is different from theirs; for he who does me a service in order that by means of me he may do himself a service, has not given a benefit, because he has made me an instrument for his own advantage. But in the case of the sun and the moon, even if they do us a service for their own sake, yet their purpose in doing the service is not that by means of us they may do themselves a service; for what is there that we can possibly bestow on them?