Naturalistic fallacy

The naturalistic fallacy is the alleged logical fallacy of believing that moral goodness is (is identical to) any simple or complex natural property, or of defining 'goodness' in terms of any simple or complex natural property. The stock example of a natural property is pleasure; ethical hedonism, for example, which is the view that everything good either is or results in pleasure, might (but need not) be construed as a definition of 'good' in terms of a natural property. On that construal, the ethical hedonist would be said to have committed the naturalistic fallacy.

It is, as is well known, entirely contentious to call the view in question a fallacy; to do so begs the question in favor of ethical non-naturalism. It was so called by G. E. Moore in his Principia Ethica, on grounds that the view always rested on a mistake--an instance of the so-called paradox of analysis--that was brought out in Moore's famous open question argument. (Details of this need to be swiped from ethical non-naturalism.)

See open question argument; ethical non-naturalism; meta-ethics; value theory; G. E. Moore.