In defense of ethical non-naturalism, philosopher George Edward Moore first coined the naturalistic fallacy. Moore argues that concept of good, has an intrinsic values that are essentially indefinable because it cannot be reduced to any natural properties. Moore adds that even by reducing the concept of good to divine or supernatural command is the equivalent to stating its naturalness. In Principia Ethica, Moore describes good as "one of those innumerable objects of thought which are themselves incapable of definition, because they are the ultimate terms by reference to which whatever is capable of definition must be defined." Hence, any attempt to define good will result in a circular definition (i.e., good is a concept that is self-referential).
The naturalistic fallacy is committed, according to Moore, when one makes arguments that conflates or relates non-natural concepts such as good, with natural concepts such as pleasure, need, survival, natural processes, or (as mentioned) even divine command.
Should the naturalistic fallacy actually be considered an error in logic? If it is, then the ramifications in moral philosophy are fairly extreme: it moots any ethical argument that centers around the concept of goodness. That said, should the concept of good be considered when discussing ethics? If so, how can one justify centering an argument around a concept that is not semantically coherent?