"That all men wish to be happy is a certitude for anyone who can think." So opens Book X, and so is Augustine's philosophy defined in a single sentence. And so in one sense his legitimate heir is self-professed Christian Hedonist John Piper ("Everyone wants to be happy, it influences everything we do..."). Or, as the old Anglican Jeremy Taylor said, "God threatens terrible things, if we will not be happy." Over and over Augustine has hammered home the point that while the Platonists rightly realize that such happiness as will satisfy the human soul can only come from the one true God, they fail to achieve this happiness because they interpose demons as mediators between God and man.
But what about angels? Should we at least treat the good spirits as objects of reverence?
In response, Augustine enters into a semantic discussion where he gives a nod to the Greek (not his strong suit), but relies heavily on his own native Latin. The general point is that sometimes the same word can be used in different ways. We might think of it like this in English: "I honor God" ≠ "I honor my parents." Even though I use the same word, I do not mean the same thing.
"Religio", Augustine points out, can mean "worship of God" in Latin, but it can also mean "the binding force of human relationships." So while the same word is used in a sentence, we must not therefore assume that we have the same meaning. Augustine could have "religion" with both God and man without meaning that he is worshiping God and man alike.
So, when we say we "reverence" the angels or the saints, we do not mean that we worship them as we worship God. We mean that we honor them as sharers in heavenly fellowship. I do not go to an angel for intersession, I see an angel as portrayed in Scripture as a being whose existence is rooted in delight in and obedience to God. From their point of view, Augustine points out, "if they love us and desire our happiness, then, indeed, they will wish our happiness to flow from the same source as theirs. For, how could our happiness have any other source than theirs?" Do we worship angels? No! Do we look at them as a model of obedience? Absolutely!
So far we're still in agreement with the best of the neo-Platonist philosophers (Augustine specifically engages Plotinus). Even when they get weird and pantheist and say things like "the rational soul of the universe", they understand that any Light in that soul comes directly from God Almighty. So when we see John the Baptist described we see a man who was "sent from God" who "was not himself the Light, but was to bear witness to the Light." God and God alone is the source of light and truth and reason, we must not look to created beings for our help but must instead turn (as these beings will tell us) to the Source Himself.