Morals are the only proper subject of philosophy; for these inquiries are practicable and useful, but the discussions about nature are quite the contrary, neither being comprehensible, nor having any use, even if they were clearly understood.
For it would be no advantage to us, even if we could with our very eyes survey the whole world, and the nature of all beings, of whatever kind that is. For we certainly shall not be on that account wiser, or more just or brave or temperate, nay, not even strong, or beautiful, or rich, without which advantages happiness is impossible.
Wherefore Socrates was right in saying that of existing things some are above us, and others nothing to us: for the secrets of nature are above us, and the conditions after death nothing to us, but the affairs of human life alone concern us.
Eusebius – Praeparatio Evangelica