In January this year, would-be Republican Presidential candidate Rick Santorum met with a hostile response from college students in New Hampshire when he raised the issue of polygamy in response to a question about same-sex marriage:

“If it makes three people happy to get married, based on what you just said, what makes that wrong?”

His questioner replied with the calmly delivered and radically incisive analysis that is typical of the present debate:

“That’s irrelevant. In my opinion, yeah, go for it. But what I’m asking you is how do you justify your beliefs based on these high morals you have about all men being created equal?”

I remember being taught in a class on bioethics that many of the arguments used against euthanasia, drug legalisation and other highly controversial policies were invalid because they relied on metaphors. You’ve heard them all before: ‘the thin end of the wedge’, ‘a slippery slope’, ‘foot in the door’, ‘the camel’s nose’, ‘open the doors’, ‘open the floodgates’, and so on. It is typical, for example, to find opponents of euthanasia arguing that even the most restrictive and careful euthanasia regime will eventually lead to the more expansive and unrestricted practice of euthanasia. Such arguments flourish because they are easy to mount yet difficult to rebut, and because – in a society heavily influenced by consequentialist arguments – they appeal to fearsome and dangerous consequences.

Against such an argument the euthanasia advocate has limited options. He can: (a) put his hand on your shoulder, look you in the eye and say “Trust me. We won’t let that happen”; (b) repeatedly emphasise the word ‘safeguards’ at every available opportunity; or (c) launch a counter-attack with a wearied and dismissive critique of ‘slippery slope’ arguments.

Option (c) has proven quite successful. Challenging the very notion of a ‘slippery slope’ is a potent move because it forces opponents to elaborate their argument beyond the simple and appealing metaphor. ‘Slippery slope’ arguments are extremely difficult to defend without relying on metaphoric images of a gradual descent into an unwanted moral chaos. “I said ‘open the floodgates’! How much clearer could I be?”    

Whether the issue be euthanasia or same-sex marriage, a slippery slope argument that ‘X will lead to Y’ can always be countered by the simple particular assertion: ‘X is the issue. Nobody is talking about Y; why, oh why, won’t you stop talking about Y?’

So when conservative Melbourne columnist Andrew Bolt raised the spectre of polygamy in the context of the same-sex marriage debate late last year, he was a little self-conscious in his invocation of the dreaded metaphor. Bolt’s ‘Gay marriage push is a slippery slope’ carried the defensive admission that:

‘Yes, this is the slippery slope argument that social “reformers” sneer at, arguing we’re smart enough to know how much is enough when we start smashing.’

Bolt’s article ‘opened the door’, so to speak, to a swift rebuttal from a rival publication under the very efficient heading ‘Do I really need to explain to Andrew Bolt why the “slippery slope” is a logical fallacy?’ Despite describing the contents of Bolt’s article as “some hilarious dumb”, the author conceded:

‘I doubt Andrew Bolt is really stupid enough not to understand why the “slippery slope” is a fallacy. Which begs the question, then – why does he run an argument he knows is misleading and false? What is he trying to do?’

This exchange provides a great insight into a collision of worldviews. For the supporter of same-sex marriage, a ‘slippery slope’ argument invoking polygamy is a complete non-sequitur, like some kind of bizarre word-association game: ‘you say tomato, I say prosthesis.’ Indeed, given the philosophical consensus that ‘slippery slope’ arguments are not, in fact, logical arguments at all, the supporter of same-sex marriage might be forgiven for thinking that polygamy is being invoked purely and cynically to scare the public.

More than a scare tactic

The problem with this point of view is that it fails to appreciate the many and varied ways in which ‘slippery slope’ scenarios (as opposed to arguments) actually function. Indeed, an excellent paper by UCLA Professor of Law Eugene Volokh from 2003 undertook the noteworthy task of demonstrating actual mechanisms that underlie the various ‘slippery slope’ metaphors.

Volokh discussed mechanisms such as ‘cost-lowering’, ‘attitude-altering’, ‘small change tolerance’, ‘political power’ and ‘political momentum’ as examples of mechanisms whereby X can in fact lead to Y.

One intriguing example is that gun registration – itself a seemingly innocuous practice – could ‘lower the cost’ for government control and restriction of gun ownership. A similar example from the world of bioethics is that IVF technology ‘lowered the cost’ for research on human embryos and human cloning. Not only did IVF ‘lower the cost’, it was also ‘attitude-altering’ in terms of public, scientific, and legislative willingness to accept the concept of human life being created (and eventually destroyed) in laboratories.

In ethical issues the journey from X to Y takes place primarily on the level of principle, and for most of us these principles are hidden away behind layers of passion, emotion, culture, and social mores.

Take, for example, the issue of slavery: very few people are in favour of slavery these days. Yet we know for a fact that this was not always the case. Transport the average Anglo-Saxon of anti-slavery orientation back in time by about 200 years and we might find to our shock and horror that his enlightened moral views are out of step with mainstream society.

Take the average anti-whaling Aussie back less than a hundred years and his views on the subject will likewise clash with that relatively recent social context. These obvious moral discrepancies should elicit doubt from those of us who presume that our moral values are self-evidently true. If we cannot say why slavery is wrong, or why whaling is morally objectionable in principle, then we might merely be parroting the popular values of our present social context.

Which is more strange: that people once accepted slavery, or that they now reject slavery as though it were unthinkable to do otherwise? This is lesson one: human beings can adapt and acclimatise to even the most morally depraved acts and situations, to the point where they are considered normal. What this means is that even if we decide to adopt something novel and potentially fearsome such as euthanasia with a host of restrictions and safeguards, the novelty and the fear will soon dissipate and wear off. In time, restricted euthanasia (perhaps for cases of terminal illness only) would be accepted as normal, perhaps a ‘necessary evil’. We cannot help but become acclimatised to it.

This brings us to lesson two: human beings are rational creatures. Try rewarding children or employees on an entirely arbitrary basis, and you will immediately discover the awesome logical power of the human mind.

I dare you to arbitrarily let one employee take the afternoon off, and then endure the dark scowls and conspiratorial muttering of all the others. What they want are reasons: ‘why did he get the afternoon off?’ ‘why can’t I go too?’ . We all know that notwithstanding evidence of sheer insanity or meaningless frivolity, human beings act according to reasons.

Acting reasonably

This dependence upon reasons is a function of that superordinate thing we appropriately name reason. Our actions have their reasons because we act according to reason itself. They may not be good reasons, consistent reasons, or even enduring reasons; but reasons we have, and we thus, from the same etymology, distinguish ourselves by the term rational beings.

With regard to euthanasia: it would only be a matter of time before someone who did not meet the narrow requirements of a limited euthanasia regime demanded reasons for this discrimination. The onus would then be upon society and its lawmakers to prove the consistency and merit of their reasons for allowing euthanasia in one set of circumstances but not in another, perhaps very similar, set of circumstances. What is it about terminal illness that warrants euthanasia where severe disability or chronic illness do not? How can we arbitrarily allow ‘relief’ for one set of people in suffering, while denying ‘relief’ to those whose suffering might actually be worse?

We have seen this exact progression unfolding through the legal status of abortion in some jurisdictions. In countries such as Britain and Australia, abortion was originally unlawful in all circumstances. Exceptions were made in case law, originally for the sake of ‘preserving the life of the mother’. This exception was subsequently interpreted in Australia to mean ‘to preserve the woman from a serious danger to her life or her physical or mental health”’ This judgement was in turn expanded to include ‘any economic, social or medical ground or reason’ to avoid the aforementioned dangers.

Finally, an additional judgement extended the range of these considerations and danger to include not just the duration of the pregnancy but any point in the mother’s life. Not to be outdone, in 2008 one Australian state parliament removed abortion prior to 24 weeks from the criminal code entirely. There is a logic to this expanding circle of legal exceptions; and at each stage the compelling reasons for change are made more plausible by the normalisation, the acclimatisation that has gone before it. 

These two features of humanity – our reason and our capacity for acclimatisation – are the core elements of what we generally consider a ‘slippery slope’ scenario. Reason alone is not enough. If same-sex marriage is permitted in this country, we will not be compelled by force of reason alone to consent to polygamous marriages. To this extent the slippery slope sceptics are in the right.

But if we look at the process by which same-sex marriage has gone from self-evidently nonsensical to a seemingly ‘inevitable’ social change, we can see that this progress has been achieved through a formidable process of social acclimatisation and normalisation. If anyone had suggested 50 or so years ago that the modern gay rights movement would lead to same-sex marriage, he would have been accused of a cheap and convenient ‘slippery slope’ argument. Yet here we are today, on the verge of redefining marriage to include same-sex couples because (1) we now consider homosexuality to be normal, and (2) we struggle to find any reasons to deny marriage to same-sex couples. When people claim that same-sex marriage will ‘lead to’ polygamous marriage, they are pre-empting the application of these same two faculties – acclimatisation and reason – to the issue of polygamy.

We know for a fact that there are people who wish to practice polygamy with legal recognition. We know that given sufficient time to build up public sympathy and awareness, their cause can be normalised. If we now demonstrate our willingness to redefine marriage for the sake of same-sex couples, what reasons will we offer for denying similar privileges to polygamous groups in the future?

There is nothing, in principle, to stop us from arbitrarily allowing same-sex marriage but rejecting polygamy. There is nothing to stop us from arbitrarily restricting euthanasia to very narrow circumstances, if we so choose. The problem is that as our sense of ‘normal’ shifts over time, we may find ourselves wanting to shift those arbitrary boundaries. The only solution is to calibrate our sense of ‘normal’ by non-arbitrary principles, reasons that will not shift.

Zac Alstin works at the Southern Cross Bioethics Institute in Adelaide, South Australia. 

Zac Alstin is a writer, editor and stay-at-home dad to three marvellous children, in Adelaide, South Australia. His hobbies include martial arts, making things at home, and contemplating the underlying...