You’re Doing it Wrong, part 1: The Naturalistic Fallacy

This is the first installment of what I hope will be a series of posts (probably not consecutive) on logical fallacies. Logical fallacies are a category of arguments that are never valid — they are incorrect ways of thinking. Today’s logical fallacy is the naturalistic fallacy (also called the “appeal to nature” or “Hume’s Guillotine”), which incorrectly equates what is true in the natural world with what is morally correct. 

Consider the following statements:

Eating meat is okay because humans evolved to eat meat.

Warfare is wrong because other animals don’t do it. (Some animals actually do engage in warfare, but people make this argument nonetheless.)

Homosexuality is okay because homosexuality is present in other animals.

Each of these arguments attempts to justify or condemn a moral claim based on what is or is not observed in nature. The first part of each statement (before the “because”) is an ideological claim and the second part of each statement (after the “because) is an empirical claim. Each part of each argument is valid as it is, and the opposite moral claims would also be equally valid. They become fallacious, however, when the two sides are associated. Science can only tell us what exists or what is true about the natural world — it absolutely cannot give us moral guidance.

No matter what your ideology is, you can find facts about nature that are consistent with your morals and facts about nature that are inconsistent with your morals. Some people believe that eating meat is wrong and almost everyone agrees that rape, murder and slavery are wrong. But these moral stances cannot be gained from nature, and neither can the opposite stances (that eating meat, slavery, rape and murder are morally sanctioned). Many animals eat other animals (e.g. dolphins, sharks, lions, wolves) and many don’t (e.g. cows, giraffes, horses, snails). Many animals rape (e.g. chimpanzees, chickens, orangutans, sea turtles). Some ants take slaves. Chimpanzees, langur monkeys and many other animals kill members of their own species. Nature is, as Alfred, Lord Tennyson said, “red in tooth and claw.”

There are a variety of ways the naturalistic fallacy can manifest:

1) People refuse to accept empirical findings because they are ideologically opposed to the outcome.

One time, I was explaining to someone the phenomenon that animals may kill some of their offspring when they cannot feed them all. She refused to believe it on the grounds that animals are more moral than humans.

2) People assign moral beliefs to a researcher based on the researcher’s findings.

For example, people sometimes claim that scientists studying sex- or race-differences are sexist or racist. For ideological reasons, some people like to believe that there are no differences between the sexes or among the races. When research threatens this, some people assume that the researchers making the discoveries are morally endorsing the findings. Interestingly, people don’t make this type of claim about medical researchers. When someone discovers a new form of childhood cancer, he or she is not accused of endorsing childhood cancer. Rather, it is seen as a previously unknown problem that we can choose to fix if our ideology drives us to do so. All scientific discoveries are morally neutral, and cannot threaten anyone’s ideology. Science tells us what is, not what we should do about anything, and the same goes for the scientists making discoveries. Things that are objectively true are true no matter who discovers it or what their own ideology is.

3) People claim that something is or is not moral because it does or does not exist in nature.

Many people who oppose homosexuality or gay marriage argue for their side by claiming that other animals are not homosexual. Many people who accept homosexuality and gay marriage argue for their side by pointing out that other animals ARE homosexual. Only the latter claim about non-human homosexuality is true, but both statements make the naturalistic fallacy. Science can tell us that homosexuality exists and why it exists and in what species, but it cannot tell us how we should feel about it.

There are two ways that science can interact with morality. First, science can study morality as a natural phenomenon, as some of my colleagues do. What parts of the brain are involved in morality? How is morality transmitted as an aspect of culture? Why is morality different in different areas? When these topics are studied by scientists, scientists are still not endorsing any given morality. They are not making a claim about which moral system is superior to another. They are just reporting on it as they would any other aspect of nature. (Note: humans and our morality are a part of nature.)

The second area is to determine how best to achieve one’s moral goals. For example, many people are morally opposed to war and are interested in reducing or stopping it. Science cannot justify this belief, but it can help you to understand the problem you are trying to solve and help you develop action plans for solving it. Some colleagues of mine have found that exposure to pathogens increase warfare. This finding in itself does not, of course, advocate a particular action. But if you are interested in reducing war, you could use this information to help. Conversely, if you are interested in increasing war, you could also use this information.

None of this is to say that you cannot have opinions or argue about morality — just that science cannot justify any particular moral or ideological stance.


See also:

You’re doing it wrong, part 2: Post Hoc Ergo Propter Hoc


Have a topic that you want me to cover? Let me know in the comments section.

Follow me on twitter @CGEppig


About Christopher Eppig, Ph.D.

I have a Ph.D. in biology and a passion for sharing my knowledge and understanding of the natural world with anyone who will listen. At a time where science is permeating public life more than ever, it is especially important that the public understand what science is, and how its findings intersect with their own lives. In addition to the more practical benefits of scientific literacy, I believe strongly that understanding the natural world enriches peoples lives. The man behind the curtain is not me — it is the real world, which we can discover through science, and it is beautiful. Let me show it to you.  Follow me on twitter @CGEppig. View all posts by Christopher Eppig, Ph.D.

5 responses to “You’re Doing it Wrong, part 1: The Naturalistic Fallacy

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