Peck met patients who didn’t fit a standard diagnosis but had certain recurring traits. These persons showed chronic disregard for the good of others to the point of causing grave psychological harm. They were subtly but pervasively self-centered. Their symptoms were broader than narcissistic personality disorder, but they weren’t sociopaths. They knew right from wrong. But their main shared trait was the habit of lying. They all lied constantly and effortlessly about everything—especially about themselves, to themselves. As such, they were opaque even to highly trained therapists. More important, they were opaque to themselves. For Peck, the “layer upon layer of self-deception” that “people of the lie” build up insulates them so thoroughly from truth that they no longer recognize it.

Charles Chaput, Strangers in a Strange Land