The naturalistic fallacy (also called an appeal to nature) is committed when one argues that because something happens naturally or derives from nature, that therefore it is necessary good or desirable. Though it sounds quite implausible when stated in this way, the naturalistic fallacy is surprisingly common – for example, any product which advertises itself as ‘all natural’ or containing ‘no artificial colours or flavours’ is committing the naturalistic fallacy. Other common examples of the naturalistic fallacy include arguments like:
“Evolutionarily only heterosexual sex can be selected for, because homosexual sex cannot produce offspring, therefore homosexuality is morality wrong.”
“Homosexual behaviour is found throughout the animal kingdom, and homosexual tendencies are genetically determined in some subset of the human population, therefore homosexuality is not morally wrong.”
“Medications interfere with the natural course of events and so should be avoided. It is better to allow the body heal itself all-naturally.”
“It’s natural to feel angry when people don’t treat you the way you would like, so there’s nothing wrong about feeling angry.”
Arguments of this sort are fallacious because the mere fact that something is natural or is found in nature does not mean that it is necessarily good, safe, or desirable. There are many things found in nature that are harmful and undesirable, such as smallpox, natural disasters, and malnutrition. On the other hand, there are many helpful and desirable things that are not found in nature, such as flush toilets, vaccinations, and refrigeration. Merely stating that something is natural, therefore, insufficient; one must also give specific reasons as to why that thing is good or desirable.
Naturalistic fallacy: overview from Logically Fallacious
Naturalistic fallacy: overview from Logical Fallacies