…by imposing a false world on his victims, the liar excludes them from his world. Insofar as he places them within an understanding of reality that differs from his own, he separates them radically from himself. This is what leads Adrienne Rich to observe, with poetic exactitude, that “the liar leads an existence of unutterable loneliness.” The loneliness is precisely unutterable because the liar cannot even reveal that he is lonely without disclosing that he has lied. By hiding his own thoughts, he makes it impossible for others to be in touch with him-to understand him or to respond to him as he really is, or even to be aware that they are not doing so.

Harry Frankfurt, “The Faintest Passion”