G. E. Moore - Wikipedia, the free encyclopedia
Good as indefinable
Moore contended that goodness cannot be analysed in terms of any other property. In Principia Ethica, he writes:
It may be true that all things which are good are also something else, just as it is true that all things which are yellow produce a certain kind of vibration in the light. And it is a fact, that Ethics aims at discovering what are those other properties belonging to all things which are good. But far too many philosophers have thought that when they named those other properties they were actually defining good; that these properties, in fact, were simply not "other," but absolutely and entirely the same with goodness. (§ 10 ¶ 3)
Therefore, we cannot define "good" by explaining it in other words. We can only point to an action or a thing and say "That is good." Similarly, we cannot describe to a blind person exactly what yellow is. We can only show a sighted person a piece of yellow paper or a yellow scrap of cloth and say "That is yellow."
Good as a non-natural property
In addition to categorising "good" as indefinable, Moore also emphasized that it is a non-natural property. This means that it cannot be empirically or scientifically tested or verified - it is not within the bounds of "natural science".