Definition

This fallacy arises when we infer something is good because it is natural, or something is bad because it is unnatural. The naturalistic fallacy has other meanings, but we will focus on this meaning.

Examples

1) Many people argue it is morally permissible to eat cows and pigs because it is natural. They usually argue it is natural because humans have the teeth for it, it is part of the cycle of life, or because other animals do it.

2) Some people argue homosexuality is immoral because it is unnatural.

3) It is ok to throw poo because I saw some monkeys throwing poo at the zoo.

4) We should not help the poor or weak. Survival of the fittest. 

Discussion

Even if we could prove the naturalness of eating meat, it would not necessarily be right. To see why, think of the many acts you believe to be both natural and immoral. For example, some biologists believe humans evolved natural predispositions towards rape, aggression, and xenophobia, but it does not follow they think it is morally good to aggressively rape or be xenophobic. I may be naturally violent, but it does not follow that I think it is good to act on those violent instincts. I may be born naturally self-centered, but it does not follow it is good to be self-centered.

Now consider health. Poisonous berries may be natural, but it does not follow they are healthy. Chemotherapy may be unnatural, but it does not follow it is bad.

In short, you think some natural acts are immoral and some moral, so it is logically inconsistent to argue an act is moral simply because it is natural. And it is inconsistent to argue an act is immoral simply because it is unnatural.

The vagueness of the term “natural” is another problem with appealing to naturalness or unnaturalness. The problem is people disagree about what is natural. For example, people disagree about whether homosexuality, violence, and altruism are natural. Are skyscrapers natural since they are made from natural human minds? In short, natural is a vague term that causes confusion.

How to avoid

Do not assume natural is good or unnatural is bad.  

Exercise

1. Find examples of natural acts that are good and natural acts that are bad (in your opinion). Next, find examples of unnatural acts that are good and unnatural acts that are bad.

2. Give examples of how the appeal to nature fallacy arises in debates about homosexuality, the environment, euthanasia, or other controversial issues.

3. Imagine an environmentalist argues that we should not interfere with an ecosystem because the natural order is good. Explain why this is an appeal to nature fallacy and how the environmentalist could

strengthen the argument.

Some possible answers

Answers for #1

A) Natural and immoral: It may be natural to lie, but I think it is wrong to lie (in most cases).

B) Natural and moral: I naturally feel empathy for the starving child, and I think this empathy is moral.

C) Unnatural and immoral: I think the enjoyment of torture is unnatural for most people, and I also think it is immoral.

D) Unnatural and moral: I may naturally want to strike back in revenge, but I choose the ‘unnatural’ act of nonviolent resistance and love towards my enemy.

Some people miss the point and argue that good and bad are subjective. The point they miss is that it is inconsistent for you to argue goodness can be derived from naturalness since you believe some natural acts are bad. 

2. Common Arguments: Homosexuality is moral because it is natural; Homosexuality is immoral because is unnatural.

Uncommon Arguments: Homosexuality is immoral because it is natural like violence; Homosexuality is moral because it is unnatural.

3. A better argument would consist in showing the unintended and negative consequences of disturbing ecosystems. This would not be based on a vague appeal to naturalness

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