Don't worry doc, these are natural cigarettes
Why is it so hard to make a legitimate appeal to nature?
The fundamental problem that any appeal has to overcome is that nature is just not very nice. What we describe as unethical human behavior - rape, murder, torture - are natural behaviors in at least some species (including our own). The only remarkable parts of human evil are the scale we do it on, and the thought that we might know better.
So the arguer has to somehow define "natural" in a way which excludes the parts of human behavior we don't like, yet still includes the parts we do. Humans tend to be a very package-deal sort of being, which makes this quite difficult.
One avenue is to deny that "common" means "natural". For example, while intra-species murder is common, it may still be unnatural. Perhaps only mentally deranged beings commit murder - it is not natural for mentally stable beings to commit murder. It's hard to avoid a circular definition here, and this path can't be followed for long before your definition of "natural" gets bloated to the point where your audience falls asleep.
Another path, one followed by anti-gay advocates, is to claim that "natural" means something like "normal." Psychological classifications of mental illness often include some sort of "normalcy" as a criterion, giving this more scientific backing than most fallacies can claim.
We still get problems like: it's uncommon to give lots of money to charity, is that unethical? It was pretty common to kill Jews in the holocaust, was that ethical?
One notable proponent of this view is Richard Rorty. His response was that yes, there was nothing particularly unethical about the holocaust.
Have to admire his guts, if not his conclusions.
Argumentum ex Leo
Since philosophers are so fond of giving fallacies Latin names, I would like to baptize a new one: argumentum ex Leo, or the argument from the lion. It goes something like:
- Lions eat gazelles
- Therefore, it's ethical for humans to eat meat
Why should #2 follow from #1? It seems we have two options:
- Lions are exemplary role models
- It's an appeal to nature
I could launch into a repeat of the first half of this post, but I'm sure you all see the problems with this by now. So, unless we're talking about Aslan, let's put argumentum ex Leo to rest.