Psychology doesn’t have much to say about this, though.

I draw a distinction between “Psychopath” and “Anti-social personality disorder” – once which used to be loosely supported by Psychology, but no longer is with the DSM V (one more reason to prefer Priests – at least they’re consistent). ASPD is rather simple: lack of empathy + high time preference = crime (this fails to account for moral reasoning, but then, so does dog breeding). The psychopath, however, is the constant chess player. It’s a twisted version of the “Leadership” personality – the choleric – the paranoid control freak. In a normal human being those qualities are tempered by emotiveness, which is what makes them such great leaders (the need to organize and control everything, while simultaneously caring about those under their command – and, hopefully, knowing when to let go, so as not to micromanage). In the Psychopath, they can’t stop controlling; their emotiveness is completely slaved to their intellect, with a hard-wired on/off switch. They’ll be your Best Friend in the World, so long as you’re part of their chess game; as soon as you’re no longer valuable, they don’t know you from Adam.

The Psychopath can be useful – they’re extremely adept at quickly rising up the chain, and creating organizations – and occasionally they base their persona upon ethical behaviour, so they wind up creating organizations which are doing something good – but they’re like playing with fire. Melancholics and Phelgmatics can easily fall prey to them, and wind up having their personal lives destroyed; Cholerics and Sanguines are better able to deal with them.