Morality as somehow involving RATIONALITY and impartiality received classic expression in philosophy of Kant who frankly speaks of “rational and impartial spectator” in contemplating the universal law. The overall aim of this paper is to show (1) that the idea of morality implies RATIONALITY and this will be reached at in refuting the moral scepticism; but (2) it does not necessarily indicates impartiality, since the justification of the principle of impartiality does not solve the problem of justifying particular moral principles. I will start with the question “Why should we be moral?” and then turn to moral RATIONALITY to refute moral scepticism, finally the relationship between rational morality and the principle of impartiality will be reconsidered.