One argument made against the proposal to legalise assisted dying in the UK is that making this change might result in older citizens feeling pressured to choose death, increased pressure on people to think about and defend their existence, and the inevitable acceptance of voluntary and, then, involuntary and non-voluntary euthanasia. This kind of argument can be called a slippery slope argument. A
slippery slope argument claims that if we make a proposed policy change, other changes or outcomes will occur, and because these other outcomes are objectionable, we should not make the policy change. I am generally sceptical of slippery slope arguments and in this post I wish to register some issues with their use.
Some of my doubts about slippery slope arguments are based on them so often being false. Assisted dying and euthanasia legislation is a case in point. Probably the clearest data available on the likely effects of policy changes in this area come from the Netherlands, which had some non-legislative tolerance of these practices during the late twentieth-century and legalised them in 2002. Amongst the most recent publications show that euthanasia rates in 2010 were comparable to those in 2001 and 1995, the distribution across various important categories (sex, age, diagnosis) was stable throughout this period, and, perhaps more significantly, the number of end of life decisions made without the explicit request of the patient actually declined. There are different slippery slope worries to which this data does not speak and various questions can be raised about how to interpret the data and what it shows, of course. But it surely leans in the direction of rejecting the slippery slope argument.
There is also a more general difficulty to raise about slippery slope arguments. In essence, such arguments have the following structure:
- There is an argument for adopting policy X
- X will lead to Y
- Y is bad
- The bad of Y outweighs the good of X.
- Therefore, we should not adopt X
An important point to note about this argument structure is that it does nothing to dispute 1. It could be the case that the arguments made in favour of adopting policy X are poor arguments. But the slippery slope objection does not assert this claim. In this respect, it does not dispute that there is some reason to adopt X. In virtue of this, the slippery slope argument must be understood as posing a ‘countervailing consideration’ – a reason that is supposed to stand against and outweigh the arguments for adopting X.
Adopting this form, the slippery slope argument should be thought to start on the back foot. In footballing terms, the argument begins at 0-1 (losing by one goal) and an advocate’s aim is to turn the scoreline in their favour (2-1), or, at least, to level the game (1-1). Because it has this structure, it is advocates of the slippery slope argument who shoulder the burden of proving their position. This burden of proof pertains to each of the other three premises in the argument.
In relation to 2, advocates of the slippery slope must advance some plausible reason to believe that there is a causal connection between X and Y. Quite unlike how slippery slope arguments often proceed, it is inadequate for their advocates to conjecture bad consequences. The structure of their argument – by not challenging 1 – means that it is incumbent upon them to do the work of establishing 2. Most often, proving this claim will require empirical evidence of the connection between X and Y. Sometimes empirical evidence is hard to obtain. For example, it is sometimes argued that it is difficult to know what will happen if we legalise various currently illicit drugs. But even in such cases, there will be pertinent information and theoretical modelling that can be brought to bear on the subject and the onus is upon advocates of the slippery slope to bring it so to bear. At any rate, because those who are being challenged with the slippery slope argument otherwise have the upper-hand in the debate, they should feel no obligation to disprove the slippery slope argument unless it can be shown they have a serious case to answer.
In relation to 3, it is important that advocates of the slippery slope do not merely point rhetorically to possible Ys – alleging potentially connected states of affairs and presuming they are bad. They must provide reasons that these Ys are bad. An example of this issue is the euthanasia debate worry that people will feel pressured to think more seriously about the value of their life continuing. Although many people react to such a possibility negatively, there are others who think that it would be a valuable change. The same is true of the worry that legalising assisted dying would lead to the acceptance of voluntary euthanasia. While some people worry about the latter, others are positive about it. And, in virtue of the slippery slope argument shape, the onus of showing that the best arguments point towards the posited Ys being deemed bad, again, lies on the shoulders of the argument’s advocates.
Premise 4 in the above argument is important because, in order for X resulting in Y to give reason to reject X, it is not sufficient to show only premise 3 – that Y is bad. It must also be shown that Y is bad enough to outweigh the reason to adopt X. Such an argument will often not be straightforward. For example, if legalising euthanasia is valuable because it gives many people a desired freedom to choose how to end their lives, it may not be enough to highlight that it will also increase the pressure on some other people to end their lives. We could fully agree that such pressure is a very bad thing, but still retain that it is not enough to outweigh the good we would bring to so many other lives. Something similar to this point is often made about the grave tragedy of people being run over by ambulances that are, nevertheless, permitted to drive at high speeds for the great good this permission achieves. And, once again, due to the shape of the slippery slope argument, it is the advocates of this view who must do the work of showing that the slippery slope they caution is not such a case, but, rather, one in which the bads of Y outweigh the goods of X.
It is worth noting, moreover, that advocates of the slippery slope are not obliged merely to demonstrate the plausibility of one of these claims. In virtue of the argument’s shape, they must demonstrate the plausibility of all of them. If any of 2, 3, or 4 is not adequately defended, 5 does not follow.
To some extent, the suggestion that advocates of the slippery slope provide these defences amounts to nothing more than the straightforwardly reasonable demand that those advancing views provide support for their views. But the shape of the slippery slope argument – by not challenging premise 1 – makes this demand particularly pressing. Simply put: we ought to remember that the burden of proof for premises 2-4 lies with advocates of the slippery slope and that, until they take up this challenge, the score remains 1-0 to their opponents.