Unnatural? A Fallacious Argument.

This note is about the form of a popular but fallacious argument. The instance I examine happens to be about homosexuality, but my concern here is not homosexuality, but the argument, two fallacies in the argument, and how we might avoid those fallacies.


The other day I was listening to a video by the YouTuber Noel Plum. He is someone I sometimes agree with and sometimes disagree with, but because he is generally very clear and reasonable, he is someone who has the power to change my mind.

In the video in question, which I shall not link to out of respect for him, he boasted of having changed the minds of some men about homosexuality being ‘unnatural’ by telling them a Just So evolutionary story establishing that homosexuality is a natural phenomenon established by natural (evolutionary) means.

Fallacy One

This is a well known fallacy called the appeal to nature.

Yes, homosexual behaviour occurs in nature. Not just among human beings. It also occurs in other species. So do rape, incest, cannibalism, and warfare. Being ‘natural’ is not the same as being good. As M. Scott Peck once put it, it is human nature to go to the toilet in your pants. That does not mean it is an acceptable behaviour in adults.

There are many behaviours among human beings, like wearing clothes, composing music and poetry, which have no close analogues elsewhere in nature. Their ‘unnaturalness’ does not make them bad.

There are evolutionary Just So stories about how homosexuality could be sustained in a population. We also have evolutionary accounts of how sickle-cell anæmia, cystic fibrosis, and Tay-Sachs disease (amongst others) can be sustained in a population. That does not make those diseases any more desirable.

So the first fallacy is the idea that if something occurs in nature, it is natural and therefore good, that evolution would not sustain an aspect of human physiology or behaviour if it weren’t good for us.

It would be equally fallacious to argue that something that wasn’t the result of evolution, but was purely a learned behaviour, like reading and writing, was therefore bad.

It’s a bit like the kind of advertising that claims this or that food is good for you because it is ‘natural’. So are botulism and arsenic.

How do we avoid this fallacy? By bearing resolutely in mind that nature contains many splendid and useful things and also many deadly and disgusting things, so that good and natural aren’t even close to synonyms.

Fallacy Two

The really strange thing is that the people who call homosexual behaviour ‘unnatural’ know perfectly well that it happens. If it did not happen they would have nothing to condemn. So they cannot possibly mean by ‘unnatural’ “does not occur in nature”. That means that the argument Noel Plum used to what I can only call his victims completely failed to address what they actually meant. Or supposing them to be sufficiently confused to not know what they meant (otherwise he would not have been able to trap them), what their teachers actually meant.

If it doesn’t mean “does not occur in nature”, what does it mean when some people call homosexual behaviour ‘unnatural’? (Remember, I am not arguing that they are right to do so. I am pointing out fallacies in the argument directed against the claim.)

Let’s see the two thousand year old text that probably lies behind this usage:

“Because of this God gave them up to dishonourable passions. Not only did their women change the natural use [of their bodies] to that which is contrary to nature, but also in the same way their men, having left the natural use of the women, were inflamed with desire for each other.” — Romans 1, verses 26–27.

Or in Greek,

Διὰ τοῦτο παρέδωκεν αὐτοὺς ὁ Θεὸς εἰς πάθη ἀτιμίας. αἵ τε γὰρ θήλειαι αὐτῶν, μετήλλαξαν τὴν φυσικὴν χρῆσιν, εἰς τὴν παρὰ φύσιν. ὁμοίως τε καὶ οἱ ἄρσενες, ἀφέντες τὴν φυσικὴν χρῆσιν τῆς θηλείας, ἐξεκαύθησαν ἐν τῇ ὀρέξει αὐτῶν εἰς ἀλλήλους…

So what does ‘ παρὰ φύσιν’ mean? The preposition ‘παρὰ’ has a range of meanings and is not expressible by a single English word, but in this context, the meaning that fits best is ‘away from’. (Indeed, one of the arguments some Christians give in support of homosexuals is to argue that this passage is clearly talking about people who were originally capable of heterosexual behaviour but deliberately abandoned it.)

So the real idea here is not unnatural but antinatural, something which deliberately flouts the practices that sustain humanity (and other life). Recall that the author of Romans was writing from within a culture in which human life was always precarious and it could be said that a man who did not marry had in effect murdered his descendants. As a bookseller of my acquaintance, once described by the local newspaper as the most honest man in the city, put it: “being homosexual is Nature’s way of telling you not to reproduce”.

Unless you believe that homosexual behaviour normally leads to reproduction, it seems that you have to concede that “homosexual behaviour is un[that is, anti]natural” is simply true the way the people saying it mean it.

In our times, when human life is not so precarious, some people argue that it is a moral obligation not to have children, and I would not attempt to dissuade them from remaining childless. (All the more resources for my grandchildren, thanks guys!) So the truth of the claim that homosexual behaviour is antinatural leaves its morality still open to debate.

As I said above, the issue here is the fallacy. Another example of this fallacy is what an Australian philosopher called “the silly syllogism”: if God is omnipotent he can make a stone that is too heavy for him to lift, but if he is omnipotent he can lift it. The philosopher in question offered a rival disproof of God’s omnipotence, failing to notice that (a) it had exactly the same structure as the silly syllogism, and (b) ‘omnipotence’ doesn’t actually mean what he thought it meant. See for example the Catholic Encyclopedia article on Omnipotence.

How do we avoid this fallacy? We have to first realise that words have technical and historic meanings and that our opponent in debate may not mean what we would have meant, especially an adherent to an old philosophy. And second, we have to make a serious attempt to understand what our opponent does mean, which, sad to say, requires taking seriously the possibility that they might be reasonable people saying something true.

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