Don't go out with or hang around with people like Drake. Psychopaths are even less fun than sociopaths like Caine.

Sociopathy is chiefly characterized by something wrong with the person's conscience. They either don't have one, it's full of holes like Swiss cheese, or they are somehow able to completely neutralize or negate any sense of conscience or future time perspective. Sociopaths only care about fulfilling their own needs and desires - selfishness and egocentricity to the extreme. Everything and everybody else is mentally twisted around in their minds as objects to be used in fulfilling their own needs and desires. They often believe they are doing something good for society, or at least nothing that bad. The term "sociopath" is frequently used by psychologists and sociologists alike in referring to persons whose unsocialized character is due primarily to parental failures (usually fatherlessness) rather than an inherent feature of temperament. Lykken (1995), for example, clearly distinguishes between the sociopath (who is socialized into becoming a psychopath) and a "true" psychopath (who is born that way). However, this may only describe the "common sociopath", as there are at least four (4) different subtypes -- common, alienated, aggressive, and dyssocial. Commons are characterized mostly by their lack of conscience; the alienated by their inability to love or be loved; aggressives by a consistent sadistic streak; and dyssocials by an ability to abide by gang rules, as long as those rules are the wrong rules. As Stout (2005) indicates, it only takes three of the following to be defined as a sociopath, and some common sociopathic traits include:

Egocentricity; Callousness; Impulsivity; Conscience defect; Exaggerated sexuality; Excessive boasting; Risk taking; Inability to resist temptation; Antagonistic, deprecating attitude toward the opposite sex; Lack of interest in bonding with a mate

Symptoms of sociopathy in relation to Caine Soren.

"Sociopaths are renowned for their lack of empathy for living things, to the point where they may show no remorse for harming someone. Sociopaths see people as tools at their disposal rather than human beings in their own right."
Check with a capital CHECK. How many times have we seen Caine emulate a disinterest to the emotions of others and remorselessness? He fed toddlers to coyotes because there was no reason not to. He tried to ram a helicopter full of children into a cliff. He had no qualms with getting Drake to shoot his brother in the leg, or killing Astrid and Little Pete. And probably like, a dozen other stuff throughout the series. Lack of empathy and remorselessness are one of Caine's main personality traits. Even with Diana he disregards her wishes and feelings; does he ever actually listen to any of her advice ever? Even Caine notes this in LIGHT , when he notes to himself that he didn't even consider the hell Diana must of went through in the mine (though in all fairness, the realisation shook him up a lot). As for the "seeing people as tools", well...Just look at Penny. Bug. Orsay. He refers to them akin more to objects and pawns than friends or associates.

"Sociopaths are persausive, charismatic and manipulative. They are often great at socialisation, and it is not rare for a sociopath to be regarded as charming by peers. This is a facade used primarily to manipulate."
We all saw how he worked that crowd at the beginning of GONE. And we all saw how he tricked Zil. Another check, for definite.

"Sociopaths usually exhibit worrying behavoir as children or pubescents."
Well, Caine tried to take over the world aged 14. So I think we can safely say thats a "check".

"A willingness to use violence."
Do I really have to elaborate on this one? Do i really? Caine's power is practically to throw people through walls peeps. Check.

"Sociopaths very often have egomania, or a inflated, unrealistic sense of self-worth. They may believe they are underappreciated or misunderstood."
OR A EFFING KING.
CHECK. CHECK CHECK CHECK CHECK CHECK.

"Sociopaths have been noted as having high IQs and being of above average intelligence."
In my opinion, check. Caine has done some stupid shizz in the past (Bad idea it was to upset Penny), but he certainly is exceptionally smart, both academically (implied) and in cunning (shown). He has a large vocabulary, and has shown adept understanding of sociology and the way societies work as a whole. He also has been proved to have deductive abilities, and a understanding of biology. And of course, he's also shown examples of resilience and *ahem* "creative" solutions to problems, as well as some ingenious (albeit evil) plans. So I'll have that down as a "check".

"Sociopaths are promiscuous, having trouble commiting to relationships and often having many sexual partners."
Um...I'd have to say thats one of the only symptoms Caine doesn't portray. no check. In GONE, it's remarked that while unusually charismatic for his age, Caine is ridiculously awkward around girls. And apparently, although he and Diana had been conspiring for months, he had never tried to kiss her before the final battle. I honestly wouldn't be surprised if that was his first kiss. Caine is pretty much as monogamous as they come, being exclusively interested in Diana throughout the whole series and probably before that too. In FEAR its noted by Connie how "all the girls flocked to him" but he never seemed to pay them much attention. And when Penny starts flirting with him in FEAR, even saying that she could be "Anyone you like..In your imagination" he asks for her to spare him the details. So nope, Caine is far from promiscuous. He's like one of those octopus thingys that have the same mates for the entirety of their lives. Even if they think they're a king and drive the other octopus (whos having a little octopus) to their good twins lake and away from them...That anology backfired a little.

Compulsiveness and a lack of self control. Often spontaneous.
CHECK. Oh for the love of God, check.

So...to recap; Caine is most definitely a sociopath, even though he's missing one trait.
It would seem I accidently wrote a wall of text. Sorry.