Abstract: “Liability reason” is a core concept hidden in Weber’s proposition. It is the behavioural outcome of man’s independent cognizance of self, and a moral practice ability to bear the responsibility of his own doing; it is a reason of moral practice that can turn duty into faith with passion and desire as its motive force and with the guarantee of the judgement out of reasonable consideration; and it is a modern ethics in which the ethics of liability and that of faith combine with each other, the reason of instrument and that of value support mutually, and reason and affection demonstrate affinity for each other.

Key words: Weber, ethical thinking, liability reason, moral practice reason