I’m reading Trollope’s He Knew He Was Right. Characters are constantly being described this way: “She had taught herself to believe that she had made the right choice.” The title of the novel could have been: He Had Taught Himself to Believe that He Was Right. 

That idea–that our beliefs are the product not of instinct or even logic but of a kind of impulse toward self-preservation, or self-construction, which sometimes is indistinguishable from self-delusion–seems very modern to me. And very true.