Neville Goodman’s metaphor watch: A slip-up

neville_goodmanIt was inevitable, in the recent cluster of articles about assisted dying, that the slippery slope would be mentioned. I referred to it when discussing Pandora’s Box (q.v.), and quoted Steven Poole from the Guardian: it is a “metaphor that is a logical fallacy, grossly overused, and possibly referring to the difficulty of getting uphill rather than the peril of sliding down.” I dismiss his last reason. It may be true that the phrase emerged as the difficulty of getting uphill, but objecting to its current use on those grounds is akin to demanding that decimate means to kill one in ten or hierarchy applies only to angels.

But his first two reasons stand. As Poole points out, if the law is changed to allow mitochondrial transfer, that does not in any sense allow some other, possibly grotesque, scientific manipulation of a baby’s genetic makeup. The slippery slope is “anti-rational fearmongering… that the wielder supposes to function as a knockout argument”. What is or is not allowed must be preceded by rational discussion of its risks and benefits, though that is becoming less easy in this time of instant offence and manufactured outrage.

For all that Poole thinks slippery slope overused—and I agree with him—there are only about 200 in PubMed®, and some of those are physical rather than ethical slopes. In a paper about cardiac repolarization, the idea was put forward that the normal may become the pathological. In another, the slope was from gestational diabetes to established diabetes.

But most slopes are ethical, and Google Scholar® gives 100 000 results. Just slippery slope logical fallacy notches up 14 000, and conjoined twins slippery slopes 17 000, so I hesitate to get too detailed or philosophical in my criticism.

My main objection is that it is a lazy argument, requiring nothing more than emotional dismissal. However, even though I am happy to apply hierarchy to any ranking by status, and not just to angels, I would be delighted to have the opportunity of taking Poole’s advice and say, “Yes, but I think we can get there if we really try!” when some “bloviating windbag complains that a proposed policy is on a ‘slippery slope’”. Bloviate is of US origin, and means (COD) to talk at length, especially in an inflated or empty way.

Neville Goodman is a retired consultant anaesthetist and a writer. He is co-author of a book on medical English.

Competing interests: I have read and understood BMJ policy on declaration of interests and declare that my only competing interest is my co-authorship of a book about medical English.