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).

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.

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

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.