Moral relativism is the doctrine that morality may vary from culture to culture. Given the difficulty of saying when two individuals belong to the same culture it can be taken in more or less radical forms. In its least radical form it means nothing more than that, although morality is fixed and universal for human beings, Martian morality may be different. In its most radical form it implies that each person has his own morality which may vary from one individual to another and from one moment to the next.