The City of God/Book III/Chapter 4
Some one will say, But do you believe all this? Not I indeed. For even Varro, a very learned heathen, all but admits that these stories are false, though he does not boldly and confidently say so. But he maintains it is useful for states that brave men believe, though falsely, that they are descended from the gods; for that thus the human spirit, cherishing the belief of its divine descent, will both more boldly venture into great enterprises, and will carry them out more energetically, and will therefore by its very confidence secure more abundant success. You see how wide a field is opened to falsehood by this opinion of Varro’s, which I have expressed as well as I could in my own words; and how comprehensible it is, that many of the religions and sacred legends should be feigned in a community in which it was judged profitable for the citizens that lies should be told even about the gods themselves.