How can a person tell whether his action is good or bad?

A person is capable of distinguishing good actions from bad ones because he possesses reason and a conscience, which enable him to make clear judgements. [1749-1757, 1757-1758] The following guidelines make it easier to distinguish good actions from bad ones: (1) What I do must be good; a good intention alone is not enough. Bank robbery is always bad, even if I commit that crime with the good intention of giving the money to poor people. (2) Even when what I do is truly good, if I perform the good action with a bad intention, it makes the whole action bad. If I walk an elderly woman home and help her around the house, that is good. But if I do it while planning a later break-in, that makes the whole action something bad. (3) The circumstances in which someone acts can diminish his responsibility, but they cannot change at all the good or bad character of an action. Hitting one's mother is always bad, even if the mother has previously shown little love to the child.