In reply to Robert Durran:
No, it's a little more than that I think
Conscience is understanding, and caring about, the consequences of our actions.
'Karma' is setting out to carry out beneficent actions, on the belief that positive events will happen to you as a result.
And is clearly mystical bollocks on one level- there is no supernatural hand guiding our fares.
But being nice to people is its own reward, which should be enough; and in a small-ish community, if people remember you were nice to them when yyou didn't need to be, they may choose to do something optional which is nice to you in future.
So for purely sociological reasons, it may not be complete bollocks after all...