Now every man who lies commits an injustice; and if
any man thinks that a lie is ever useful, he must think that injustice is
sometimes useful. For no liar keeps faith in the matter about which he lies. He
wishes, of course, that the man to whom he lies should place confidence in him;
and yet he betrays his confidence by lying to him. Now every man who breaks
faith is unjust. Either, then, injustice is sometimes useful (which is
impossible), or a lie is never useful
--St. Augustine, On Christian Doctrine, Book I,
Chapter 36
