Appeal to Nature

This is also called Argumentum ad naturam and Argument from Natural Source.

It is not the same as the Naturalistic Fallacy.

This is the claim that because a thing is natural, a secondary claim is true, typically one stating that the thing is therefore somehow good or beneficial.

The secondary claim can really be anything, i.e. that

• Activity A is morally acceptable because it's found in nature.
• Object B is good, or bad, or purple, because it has a natural origin.

A companion form of this fallacy is to say that because something is unnatural, a secondary claim is true, e.g. a thing or activity is bad.

This fallacy is often deployed in product marketing materials, specifically ones about organic products.

Examples

This tobacco is grown organically, therefore it is good for you (and not the cause of several kinds of cancer, or premature aging, or your repulsive stench.)

Monosodium glutamate comes from seaweed, which is natural, therefore it is good for you (and it is not a proven neurotoxin which accelerates the advance of Alzheimers).

Every banana contains a certain amount of naturally-occurring radioactive isotopes, but it's natural therefore you need not worry about it.

In the early days of petroleum extraction, a cure-all called Seneca Oil or Rock Oil that was largely petroleum was sold by a number of traveling con men, including John D. Rockefeller's father William. In the case of Kier's Genuine Petroleum or Rock Oil<i> the bottle touted it as A Natural Remedy.

Dueling natural and unnatural examples:

• Homosexuality conspicuously occurs in nature, not just among humans, therefore it is normal and beneficial.
• Homosexuality feels unnatural to Ahmed, especially when he has those feelings about Moe, therefore it is repugnant to Ahmed and he hates Moe.