Probably the most complicated and debated idea in philosophy. To Plato it was the ultimate Platonic form, and was represented by the sun in the Myth of the Cave. This sentiment is echoed by St. Augustine, who argued that all forms and things derive their existence from the good, the source of which is God. Aristotle objects to this somewhat metaphysical concept of good: he claims that there is no one good, but that there are diffent goods in varying contexts. He does, however, claim (in Nichomachean Ethics) that there is a greatest good, and that this good is the maximization of happiness. This divide has extended into modern western philosophy, with thinkers like Immanuel Kant attempting to conceive of good by a rational process, and the utilitarians (like John Stuart Mill) claiming that politics must be based on a pragmatic, mathematical calculus of good, which is often defined as pleasure minus pain. And of course there is Nietzsche, who claims that we must progress beyond notions of good and evil.

But in the (probably misquoted words of Mark Twain): “Always do right. That will gratify some of the people, and astonish the rest.”