Finally, we turn to something worthy of a response--namely, the "natural theology" of the philosophers. To that end, Augustine draws some broad limits within which he will work:
Now, if wisdom is God, who made all things, as is attested by the divine authority and truth, then the philosopher is a lover of God. But since the thing itself, which is called by this name, exists not in all who glory in the name,—for it does not follow, of course, that all who are called philosophers are lovers of true wisdom,—we must needs select from the number of those with whose opinions we have been able to acquaint ourselves by reading, some with whom we may not unworthily engage in the treatment of this question. For I have not in this work undertaken to refute all the vain opinions of the philosophers, but only such as pertain to theology, which Greek word we understand to mean an account or explanation of the divine nature. Nor, again, have I undertaken to refute all the vain theological opinions of all the philosophers, but only of such of them as, agreeing in the belief that there is a divine nature, and that this divine nature is concerned about human affairs, do nevertheless deny that the worship of the one unchangeable God is sufficient for the obtaining of a blessed life after death, as well as at the present time; and hold that, in order to obtain that life, many gods, created, indeed, and appointed to their several spheres by that one God, are to be worshipped.In other words, Augustine is not going to respond to all arguments of all philosophers, only to the best of the best who believe in divinity, believe that divinity cares about mankind, and who yet still deny the one true God.
Really, this means Plato.
In this chapter, Augustine gives us a quick overview of pre-Socratic philosophy as a lead-in to Plato, focusing especially on Thales and his descendants who focused on the nature of reality (the category the ancients would have called 'Physics.')
Socrates was reputedly the first to have turned philosophy from contemplation of the universe to human moral reform, and this so that by living a pure life human beings could understand and relate to the one true God, by whose will, intellect, and power alone the universe moves--though it may also have been that Socrates was just tired or the ancient version of asking how many angels can dance on the head of a pin.
Whatever his reason, Augustine suggests
For he saw that the causes of things were sought for by them,—which causes he believed to be ultimately reducible to nothing else than the will of the one true and supreme God,—and on this account he thought they could only be comprehended by a purified mind; and therefore that all diligence ought to be given to the purification of the life by good morals, in order that the mind, delivered from the depressing weight of lusts, might raise itself upward by its native vigor to eternal things, and might, with purified understanding, contemplate that nature which is incorporeal and unchangeable light, where live the causes of all created natures.Socrates proposed the idea of a "highest good" to which mankind can related. After his execution, he was followed by a number of students who all disagreed about where this highest good could be found. Some said in pleasure, some in virtue, "indeed, it were tedious to recount the various opinions of various disciples."