According to G. E. Moore, any argument which attempts to define the good in any terms whatsoever, including naturalistic terms; for Moore, Good is simple and indefinable. Some philosophers, most notably defenders of naturalism, have argued that Moore and others are wrong and that such arguments are not necessarily fallacious.
The naturalistic fallacy is an alleged logical fallacy, described by British philosopher G.E. Moore in Principia Ethica (1903). Moore stated that a naturalistic fallacy was committed whenever a philosopher attempts to prove a claim about ethics by appealing to a definition of the term "good" in terms of one or more natural properties (such as "pleasant", "more evolved", "desired", etc.).