The slippery slope argument is amongst the strongest voiced and possibly the most emotive of arguments in opposition to legalising voluntary active euthanasia (VAE, the act of accelerating the death of another, usually by lethal injection, for their own good and with their consent). In fact, in discussion on practically any change in social policy it is common place to hear objections to the effect, "if this, then that, and finally that" . But how valid is this form of argument? To answer this question, I will examine the nature of the slippery slope argument in its two major forms (empirical and logical), see how it has been applied to the debate on permitting voluntary active euthanasia and determine the validity of these applications.
It is not easy to apply a strict definition to the term slippery slope argument as it is used so loosely . The image it conjures is that of speeding hastily out of control in a direction few would want to venture without a means of stopping. A paradigmatic form of the argument is suggested by Hartough : I propose and you oppose that action A (let us say, voluntary active euthanasia) which is currently prohibited (this is not necessarily so, but is usually the case), yet is not deemed to be objectionable in itself by either you or myself and may be referred to as the top of the slippery slope
should, in fact, be permitted. Your objection arises because you believe that in allowing actions of type A, a causal mechanism exists (very much like a chain reaction) which will lead us to accept action N (e.g. the killing of incompetent patients who explicitly refuse euthanasia) which is clearly unacceptable to us both and
lies at the bottom of the slope
The nature of the links (for example, killing people who are "not terminally ill or suffering [and then] those who cannot decide for themselves" , etc.), the force or causal mechanism forming the reaction (maybe the increasing disregard for the sanctity of life) and what lies at the bottom of the slope (mass genocide) is also proposed by he who puts forward the argument.
This causal (or empirical) form of the argument is distinguished from the logical form which basically states if we were committed to being rational and consistent (supposedly held to be rather agreeable traits) in our moral reasoning we would again end up at the squalid foot of the slope; if on some rationale we accept proposition A, then by the same rationale we are committed to accepting the closely related proposition B, accept B and we are committed to accepting C and right on through to N, which is clearly unacceptable. Therefore, we should not accept A. The important difference is that while the causal form of the argument depends on a prediction that if we accept A then we will, the world being the way it is, accept N, the logical form depends on a commitment to consistency and rationality in our decision making. It is, perhaps, interesting to note that the metaphor of the slippery slope becomes somewhat less relevant in relation to this logical form of the argument. A synonym of the slippery slope argument often used is the thin end of the wedge argument' and seems to me to better convey the irresistible force (as opposed to a lack of control) of logic which forms the thrust of the argument.
A discussion of some of the slippery slope arguments opposing voluntary active euthanasia that feature in the Assisted Dying and Terminally Ill Bill (ADTIB) provides a useful framework for critically assessing the validity of such arguments. The Bill sets out provisions under which, following its enactment, voluntary euthanasia may be legally performed by a medical doctor. The provisions require that, amongst other things: it is the patient himself who expresses the wish to be assisted to die; the patient is competent, has...