Appeal to Nature
An informal fallacy where you argue that because something is “natural” it is therefore good, better, ideal, etc. While it is true that there are things in this world that are considered “natural” and also fall into the “good “ category (e.g., clean air), this isn't always the case (e.g., earthquakes). Naturalness itself doesn't automatically imply good or bad; further analysis is needed. Moreover, antipodal to the “natural” equates to a good argument is the “unnatural” equates to a bad argument. As before, something being “unnatural” doesn't automatically imply that it's bad.
Logical Form
This fallacy has a few different logical forms:
That which is natural is good, ideal, etc.
A is natural.
Therefore, A is good, ideal, etc.
Or
That which is unnatural is bad, wrong, etc.
B is unnatural.
Ergo, B is bad, wrong, etc.
Or
A is natural.
B is unnatural.
Thus, A is better than B.
Examples
The following abbreviations are used in the examples below:
PN = The Nth premise for N = 1,2,3,…. (e.g., P1 is the first premise, P2 is the second premise, etc.)
C = Conclusion
1)
P1: Organic food is grown just as nature intended unlike GMOs which have been genetically altered by science.
C: Ergo, Organically grown foods are better than GMOs.
Explanation: Here, organic food being “natural” is used to argue that these foods are better than GMO foods, which simply isn't true. Not only is the word natural nebulous in its use (i.e., what exactly is "natural" food as we've been altering the genetics of our food and changing our farming practices for millennia), but research has repeatedly shown that organically grown foods are not better than conventional (i.e., more nutritious, better for the environment, etc.) [1,2].
2)
P1: Acquiring immunity through a vaccine is completely unnatural.
C: Therefore, vaccination is wrong.
Explanation: While it is true that vaccines allow an individual to acquire immunity without actually getting the disease (i.e., the “natural” route), this isn't a good argument for not vaccinating. Many of the diseases that vaccines protect us against are quite virulent (e.g. small pox), which means that there's an uncomfortably high chance that you may not live through the disease to acquire the immunity. Note, in this case, it is easy to infer what the term “unnatural” means, which is not always the case.
3)
P1: The climate has been changing since the beginning of time. There are periods of warmth, more temperate periods such as what we have now, and then there are ice ages.
C: Thus, to think that global warming is anything out of the ordinary or something that the world should be concerned about is alarmist.
Explanation: The appeal to nature fallacy here is a bit more subtle. The argument doesn't actually use the word “natural” anywhere, but it does use the phrase “the climate has been changing since the beginning of time” which communicates the same message. That said, yes, it is true that the climate varies naturally and that we are in a current warming trend. However, the degree to which the planet is currently warming is 170 times that of which it would be without human activity [3]. This rate of change in warming is so quick that there's a real possibility that entire ecosystems could collapse as they're unable to cope with the rapid change. Further, just as humans are responsible for creating this current rapid warming trend, we are responsible for fixing it.
4)
P1: Medical Cannabis is natural and an effective treatment for almost any condition.
C: Hence, it should be physicians' first choice for treatment when a patient presents with a condition that it can treat as other drug options have side effects.
Explanation: In this scenario, “natural” is being used to argue that medical Cannabis is some sort of panacea without side effects. Both of these assertions are not true. Yes, Cannabis can be used for some conditions (certainly not “almost any”), but it isn't free from side effects [4]. As with any medical intervention that actually works, there's always going to be the possibility of side effects that must be monitored for.
Conclusion
As is always the case, if you find yourself confronted with this fallacy in everyday discourse, it is important to remember that it renders the argument bad and should be rejected. What is more, if you find yourself using this fallacy within one of your own arguments, as an individual who ascribes to the philosophy of Critical Thinking, you must replace it with a good argument.