The proud man is sincere, and, in the bottom of his heart, is convinced of his own superiority
 Adam Smith, The Theory of Moral Sentiments (1759). copy citation

Context

“two words, of which the latter always, and the former for the most part, involve in their meaning a considerable degree of blame. Those two vices, however, though resembling, in some respects, as being both modifications of excessive self-estimation, are yet, in many respects, very different from one another. The proud man is sincere, and, in the bottom of his heart, is convinced of his own superiority; though it may sometimes be difficult to guess upon what that conviction is founded. He wishes you to view him in no other light than that in which, when he places himself in your situation, he really views himself.” source