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Those Slippery Slope Arguments.

It\’s usually identified as a logical error, the use of the slippery slope argument. If we allow X to happen, then Y and Z will follow, with the proposer using as an example of Z something that pretty much everyone will reject. The aim is to gather support for not doing X, of course.

It really only works (in logic that is) when Y and Z really will inevitably follow from X, rather than is usually the case that Y and Z might, but won\’t necessarily.

It was Bernard Levin who rather refined the logical argument, calling it the Fallacy of the Altered Standpoint. It isn\’t that Y and Z will necessarily follow from X, but that if you\’re already allowing X to happen, then it doesn\’t seem that much of a step to Y or Z.

Examples Levin used abound: the original Abortion Act limited the time period that any fetus could be aborted in. Later ones have allowed abortion up to birth itself in cases of severe abnormality to the child. The late 1960s would not have, at least I don\’t think it would have, supported the contention that a 37 week Down\’s Syndrome fetus was not a human being, or rather a being with no rights at all. The 90s, when the law was changed, did.

This isn\’t to say that one view or the other is "correct", only that the latter situation came about only because of the earlier acceptance of abortion itself. A slippery slope, an Altered Standpoint.

Much is made these days of the merits of assisted suicide and one of the arguments, one I\’ve deployed myself, is that that fine line between requesting such assistance and having it forced upon you will be crossed if we do indeed allow the first part, the assisted suicide. This argument is, of course, pooh poohed, it is Tim simply using that logical fallacy, the slippery slope argument.

Mr Tommelein, whose party is a key member of Belgium\’s coalition government, has pledged to bring forward new legislative proposals extending euthanasia to children and old people suffering from such severe dementia that they are unable to choose for themselves.

Oh yes?

The old and the mad will be done away with on the grounds that they cannot choose for themselves?

There is a certain dark humour in the next paragraph of the report:

"We will seek, as Liberals, parliamentary majorities," Mr Tommelein said.

Clearly this is "liberal" in the Vladimir Zhirinovsky sense. But how did it come to this, that the vulnerable shall be done away with as simply inconvenient?

There are more than 39 cases of euthanasia declared by doctors in Belgium every month, but the true figure is thought to be double that.

Euthanasia is currently permitted on infants and more than half of the Belgian babies who die before they are 12 months old have been killed by deliberate medical intervention.

In 16 per cent of cases parental consent was not considered.

Well, if you\’re already at the Standpoint that you can and should kill babies without even asking the parents, it\’s not all that much of a leap to kill the mad without asking them, is it?

Slippery slope arguments may indeed often be logical fallacies. Doesn\’t stop some of them being valid though.


5 thoughts on “Those Slippery Slope Arguments.”

  1. But then it’s not a logical fallacy any more: it’s only a logical fallacy when Z is not an inevitable consequence of X.

    More importantly, there is a further logical fallacy in the usual rebuttal. A rebuttal of the form “that is a slippery slope fallacy” would be fine, but that’s not normally how it’s presented. It usually appears as “Z *won’t* happen as a result of X” which is to deny that there will be any progression at all, not that it is not inevitable.

    So if you can show that Z is already happening, then we ought to be making a fuss about it: the “Z *won’t* happen as a result of X” is clearly untrue.

    We need to stop Z right now, and seriously reconsider how much X is going on.

  2. No one who has brought up children can honestly witter about the “slippery slope fallacy” can they?

  3. I didn’t phrase that well. What I mean is that the Worstall/Levin point is about explaining an empirical observation, an observation that must be known to any parent. The “fallacy” business is about a point of logic that a 14 year-old would find trivial and obvious.

    Tim adds: Possibly useful to note that neither Worstall nor Levin have brought up any children….

  4. I haven’t brought up any children either. Personally.
    And I have never killed any. Personally.

    I hate to think of terminally ill folk having to suffer severe pain, with no prospect of respite or comfort.

    But I also hate to think of children, however afflicted, being denied the chance of whatever improvement medicine may be able to provide in the future. And when they are allowed to die, against the wishes of their parents, that enrages me.

    We need something. Perhaps a tribunal to hear each individual case. With the remit to take into account first, the wishes of the patient, second, any living will provisions, third, the wishes of the family, and finally, clinical prognosis.

    Cost of treatment should be inadmissible.

  5. As someone who has taught logic, I’ve never been happy with the slippery slope argument being included as a logical fallacy.

    Despite what Tim says in his last sentence, it isn’t valid. It isn’t ever valid — in the strict sense where validity means a conclusion that is entailed (ie. guaranteed) by its premises.

    That might seem to make it a logical fallacy, but it isn’t really. It’s only a logical fallacy if the person who presents it intends it to be a valid deductive argument, ie. an argument whose conclusion is entailed by its premises.

    But SS arguments are rarely presented as though they are deductive arguments. Usually they’re presented as inductive (non-demonstrative) arguments, where the premises are supposed to confer a fair degree of probability or likelihood to the conclusion, without guaranteeing it.

    In that case, the fact that the argument isn’t deductively valid is, as Dearieme suggests, irrelevant, and it is a logical fallacy in itself to claim that the argument just presented is a logical fallacy. (Whether the particular version of this argument itself is any good is another matter, as it depends on various other factors/implicit premises).

    So Tim is right to insist that he is not making any logical errors.

    What’s also annoying is that people who loudly decry SS arguments as logical fallacies when they don’t like the conclusions will use them when it suits them (because everyone who argues about politics uses them).

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