Wikipedia says:

Psychopathy is currently defined in psychiatry and clinical psychology as a condition characterized by lack of empathy ^{[1] [2]} or conscience, and poor impulse control ^{[3] [4]} or manipulative behaviors.^[5] It is a term derived from the Greek psyche (soul, breath hence mind) and pathos (to suffer), and was once used to denote any form of mental illness, often being confused with psychosis. The term is often used interchangeably with sociopathy and antisocial personality disorder^[6], but many authorities in the fields have argued that there are important differences among the three (see sect. 6 below).

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 I heard something about something or other yesterday on my drive home, and the discussion about a psychopath struck me; I only had a vague understanding of the true meaning of the term.

Do you know anyone like this?

Wikipedia continues, of course, and it is fascinating. I excerpt:

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[edit] What is a psychopath?

The prototypical psychopath has deficits or deviances in several areas: interpersonal relationships, emotion, and self-control. Psychopaths lack a sense of guilt or remorse for any harm they may have caused others, instead rationalizing the behavior, blaming someone else, or denying it outright. Psychopaths also lack empathy towards others in general, resulting in tactlessness, insensitivity, and contemptuousness. All of this belies their tendency to make a good, likable first impression. Psychopaths have a superficial charm about them, enabled by their low self-consciousness, a willingness to say anything without concern for accuracy or truth. This extends into their pathological lying and willingness to con and manipulate others for personal gain or amusement. The prototypical psychopath’s emotions are described as a shallow affect, meaning their overall way of relating is characterized by mere displays of friendliness and other emotion for personal gain; the displayed emotion need not correlate with felt emotion, in other words. Shallow affect also describes the psychopath’s tendency for genuine emotion to be short lived and egocentric with an overall cold demeanor. Their behavior impulsive and irresponsible, often failing to keep a job or defaulting on debts.^[25]

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Wow. Most people could probably identify with a piece of this here or there, but the whole just sounds superhuman, in a way.}