Good and bad
Good or right (kusala) is the quality of being ethically helpful, skilful and conducive to enlightenment, while bad or wrong (akusala) is the opposite of this. Buddhism uses three principles to determine the ethical value of any behaviour. (1) The instrumental principle is the idea that something is good if it assists in the attaining of a particular goal and bad if it does not. The goal of Buddhism is enlightenment or Nirvāṇa and so anything that is conducive to that can be said to be good. (2) The consequential principle is the idea that we can determine the value of an act by the consequences it has. Stealing, for example, leads to inconvenience, anger and increased suspicion in the victim. It reinforces lack of restraint in the thief (if not caught) and may end in punishment (if caught). All this is negative and, therefore, stealing is wrong. (3) The universalization principle is the idea that we can determine the value of something by knowing how we feel about it and then applying that to others. I would like someone to help me when I am in trouble, I can infer that others feel the same and, therefore, when I see someone in trouble I try to help them. In Christianity this concept is called the Golden Rule. No one of these principles is adequate in itself to determine good or bad, but taken together they constitute a reliable guide to ethical behaviour.
The Nature of Buddhist Ethics, Damien Keown, 1992.
