Alleged fallacy, identified by Moore in Principia Ethica (1903), of identifying an ethical concept with a ‘natural’ concept, or description of the features of things in virtue of which they are supposed good or bad. Thus if one’s standard is utilitarian, to say that some action is good will mean the very same as saying that it creates more happiness than rival actions would. This equation of meaning is almost certainly wrong, but subsequent work has not confirmed that Moore’s opponents, particularly J. S. Mill, made the identification or committed any error of reasoning based on it. See also open question argument.