Profs at Harvard uni say they have discovered a crucial meta-physiological effect. Being extremely good and moral - or conversely highly evil - actually confers mental and even physical powers on a person.

"People perceive those who do good and evil to have more efficacy, more willpower, and less sensitivity to discomfort," says psychologist Kurt Gray of Harvard. "By perceiving themselves as good or evil, people embody these perceptions, actually becoming more capable of physical endurance."

Rather than those naturally endowed with superior abilities having the potential to achieve great things for good or evil, says Gray, it is more the case that being very pure or deeply villainous confers corresponding powers.

In Star Wars style, giving vent to hatred, vengefulness and lust for galactic dominion will permit one to motivate underlings or even perhaps throttle them merely by mental force: conversely, achieving zen-like detachment in the service of the greater good might offer less impressive Jedi style abilities.

"Gandhi or Mother Teresa may not have been born with extraordinary self-control, but perhaps came to possess it through trying to help others," argues Gray.

The Harvard egghead bases his assertions on studies in which subjects were given a dollar and offered the choice of donating it to charity or selfishly keeping it. It turned out that the charitable types were then able to hold up a 5lb weight significantly longer than those who sniggeringly trousered the cash.

Similarly, other subjects who wrote stories in which they did good deeds turned out to be noticeably stronger than those whose tales depicted them neither harming nor helping others.

Worryingly, though, test subjects who wrote stories in which they figured as baleful malefactors turned out to be even stronger than the goody-goodies.

"Whether you're saintly or nefarious, there seems to be power in moral events," Gray says.

There's truth, then, in Sir Galahad's lines in Tennyson, where he states that "my strength is as the strength of ten/because my heart is pure".

But it would seem that there's power to be gained, too, down the possibly quicker, easier, more seductive other path.

And the destiny of those who sit on the fence and refuse to commit - doing no evil, perhaps, but doing no real good either, for instance like certain major search providers - is to be little more than pawns or collateral damage in the eternal battle between good and evil.

Gray's research is published in the journal Social Psychological and Personality Science. ®