Appeal to nature is a fallacy of relevance consisting of a claim that something is good or right because it is natural, or that something is bad or wrong because it is unnatural or artificial. In this type of fallacy, nature is often implied as an ideal or desired state of being, a state of how things were, should be, or are: in this sense an appeal to nature may resemble an appeal to tradition.
Several problems exist with this type of argument that makes it a fallacy. First, the word "natural" is often a loaded term, usually unconsciously equated with normality, and its use in many cases is simply a form of bias. Second, "nature" and "natural" have vague definitions and thus the claim that something is natural may not be correct by every definition of the term natural; a good example would be the claim of all-natural foods, such as "all-natural" wheat, the claimed wheat though is usually a hybridised plant that has been bred by artificial selection. Lastly, the argument can quickly be invalidated by a counter-argument that demonstrates something that is natural that has undesirable properties (for example aging, illness, and death are natural), or something that is unnatural that has desirable properties (for example, many modern medicines are not found in nature, yet have saved countless lives).
Generic forms of an appeal to nature are:
- "X is Y because it is natural." (Y being a desirable property)
- "X is Z because it is unnatural." (Z being an undesirable property)
Or simply when a desirable or undesirable property is implied:
- "X is natural."
- "X is unnatural."
This fallacy is exemplified, for instance, on some labels and advertisements for alternative herbal remedies. The labels often have the phrase "all-natural" to assert that the product is safe. The idea that natural herbs and plants are always safe ignores the many toxic plants found in nature (hemlock, nightshade, belladonna, poisonous mushrooms, to name a few) and any possible side effects the herbs might have. Cocaine, for instance, is an "all-natural" medicine derived from the coca plant, and which was prescribed for many years for everything from chest colds to depression, yet it is highly addictive and can wreak havoc on the body's organs. Whether a product is "all-natural" or not is irrelevant in determining its safety or effectiveness.
The presence of this fallacy is manifest in the logic behind certain objections to evolution, specifically objections to evolution's morality. Those who object for this reason assume that if behaviors such as polygamy, infanticide and violence are shown to be natural, that would make them acceptable. This misunderstanding has fueled some animosity towards evolutionary biologists, for example sociobiology was criticized from this angle in the latter half of the twentieth century. (See also sociobiological theories of rape.) Others, while not believing 'natural' to be 'right' themselves, assume that those advancing evolutionary theories do. This objection should not be confused with the closely related criticism that biologists in these fields are suggesting genetic determinism. This fallacy is often present in arguments for the legalization of marijuana or other drugs such as peyote. This excludes, of course, legalization arguments that use the methods of biochemistry and medical science to weigh the effects of marijuana and peyote.
- Naturalistic fallacy - a related fallacy often assumed to mean the same thing.
- Science of morality