"I take it that conscience is the guardian in the individual of the rules which the community has evolved for its own preservation. It is the policeman in all our hearts, set there to watch that we do not break its laws. It is the spy seated in the central stronghold of the ego. Man's desire for the approval of his fellows is so strong, his dread of their censure so violent, that he himself has brought his enemy within his gates; and it keeps watch over him, vigilant always in the interests of its master to crush any half-formed desire to break away from the herd. It will force him to place the good of society before his own. It is the very strong link that attaches the individual to the whole. And man, subservient to interests he has persuaded himself are greater than his own, makes himself a slave to his taskmaster. He sits him in a seat of honour. At last, like a courtier fawning on the royal stick that is laid about his shoulders, he prides himself on the sensitiveness of his conscience. Then he has no words hard enough for the man who does not recognise its sway; for, a member of society now, he realises accurately enough that against him he is powerless."
from "The Moon and Sixpence" by Somerset Maugham