Appeal to nature

An appeal to nature is an argument or rhetorical tactic in which it is proposed that "a thing is good because it is 'natural', or bad because it is 'unnatural'". It can be a bad argument, because the implicit (unstated) primary premise "What is natural is good" typically is irrelevant, having no cogent meaning in practice, or is an opinion instead of a fact. In some philosophical frameworks where natural and good are clearly defined in a specific context, the appeal to nature might be valid and cogent.

General form of this type of argument:

That which is natural, is good.
N is natural.
Therefore, N is good or right.

That which is unnatural, is bad or wrong.
U is unnatural.
Therefore, U is bad or wrong.

In some contexts, the use of the terms of "nature" and "natural" can be vague, leading to unintended associations with other concepts. The word "natural" can also be a loaded term – much like the word "normal", in some contexts, it can carry an implicit value judgement. An appeal to nature would thus beg the question, because the conclusion is entailed by the premise.

Opinions differ regarding appeal to nature in rational argument. Sometimes, it can be taken as a rule of thumb that admits some exceptions, but nonetheless proves to be of use in one or more specific topics, (or in general). As a rule of thumb, natural or unnatural facts provide presumptively reliable good or bad values, barring evidence to the contrary. Failure to consider such evidence commits a fallacy of accident under this view.

Julian Baggini explains that "[E]ven if we can agree that some things are natural and some are not, what follows from this? The answer is: nothing. There is no factual reason to suppose that what is natural is good (or at least better) and what is unnatural is bad (or at least worse)."

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Wikipedia