I read last week that Democrats were complaining that the Administration's prescription-drug bill puts the nation on the slippery slope toward Medicare privatization, that the dismantling of West Bank outposts puts Israel on a slippery slope leading to its destruction, and that the ownership of a women's NBA team by a Connecticut casino sets the sport on a slippery slope towards control by gamblers.
And the metaphor was predictably ubiquitious in condemnations of the Supreme Court's overturning of the Texas sodomy law -- Jerry Falwell said it could set the nation down a slippery slope in which courts might approve bestiality, prostitution and the use of narcotics, in an echo of Senator Rick Santorum's controversial remarks of several weeks ago.
To judge from the news stories, the entire nation is coming to resemble San Francisco after a heavy rainfall. In the press, the phrase "slippery slope" is more than seven times as common as it was twenty years ago. It's a convenient way of warning of the dire effects of some course of action without actually having to criticize the action itself, which is what makes it a favorite ploy of hypocrites: "Not that there's anything wrong with A, mind you, but A will lead to B and then C, and before you know it we'll be up to our armpits in Z."
The argument goes by various names. The phrase "slippery slope" dates from the mid-nineteenth century, around the same time that people started to talk about "letting the camel's nose into the tent." That's an allusion to a fable about a camel who asks if he can put his nose into a workman's tent to keep it from the cold, and winds up inserting first his shoulders, then his legs, and so on, until he disposseses the inhabitant. (No Arab I talked to knows the fable, and I suspect it may be a Victorian invention.)*
Then there's the domino effect, an analogy that Dwight Eisenhower used in 1954 to justify US intervention in Vietnam. Or people talk about the thin end of the wedge, the snowball effect, the doomsday scenario, or opening the floodgates.1 One way or another, it always comes down to "God knows where will it all end."
The rhetoric textbooks usually describe the slippery slope as a logical fallacy, but that depends on how it's used. When you say that A puts us on a slippery slope to B, for example, you might mean only that A will create political momentum for B, or that A would make B cheaper or easier to implement. The UCLA law professor Eugene Volokh gives the example of installing video cameras at every intersection. That may make it easier to deter street crime, but it also provides the government with the means to perform more sinister forms of surveillance.2
Or sometimes the slippery slope is invoked in the course of making an argument about the impossibility of drawing clear moral distinctions -- if you can't draw the line between A and B, then how can you accept one and reject the other?3 That's an argument you always hear from abortion critics -- where does a fetus end and a child begin? It's an instance of what Greek philosophers called the fallacy of the heap, or the Sorites Fallacy. If you start with a heap of sand and take one grain away, you're still left with a heap, but if you keep repeating the process you wind up saying that a single grain of sand is a heap all by itself. The mistake is in assuming that if a distinction isn't clear-cut it can't be drawn at all.4
The Supreme Court justices love to torment advocates with slippery slope examples, in an effort to get them to clarify their positions, with the result that the Court transcripts often have the air of absurdist theater. But the technique is more disconcerting when it moves from the hypothetical to assertions of fact, the way it did in Justice Scalia's dissent in the Texas case. Acording to Scalia, once you start throwing out laws that reflect the moral choices of the majority, you undermine the basis for state laws against bigamy, same-sex marriage, adult incest, prostitution, masturbation, adultery, fornication, bestiality, and obscenity.5
I have the feeling that Scalia had a good time drawing up that list, but it isn't likely he really buys the logic -- as if the law was now helpless to distinguish between masturbation and bestiality. It's hard to imagine him voting to overturn a state anti-bestiality statute on the grounds that the Texas sodomy decision leaves him no alternative.
But the real problem with slippery slope arguments isn't their logic, but the rhetorical games people play with them -- they're a way of turning every decision into an unprecedented step into the void. In theory, you could use Scalia's logic to run the metaphor uphill -- you could just as easily say that refusing to overturn the Texas statute would open the way to laws restricting nose rings, public dancing, or other things that voters might find morally unacceptable. But nobody ever brings up the slippery slope to argue for a change in law or policy -- it's always an argument for maintaining the status quo. The English legal scholar Glanville Williams once called the slippery slope "the trump card of the traditionalist, because no proposal for reform is immune to [it]." 6
That comes from the metaphor itself, with its image of stepping off the edge of a slope. But law and policy decisions are rarely that dramatic -- it's more like carving our way along a hillside, making small adjustments as we go. Or to switch metaphors, we all agree that we want to keep the camel's nose and haunches inside the tent and leave his nether parts out in the desert -- the question always comes down to where we want to put the hump.
1. These arguments are sometimes distinguished on various logical grounds, but usage generally plays fast and loose with all these terms. For a discussion of the varieties of the slippery slope and its analogues, see Douglas Walton, Slippery Slope Arguments, Oxford University Press, 1992. return
2. As Volokh notes, there are any number of other possible relations between A and B short of strict causality -- A might create a political climate congenial to B, or create a legal precedent for B. See "The Mechanisms of the Slippery Slope," Harvard Law Review, February, 2003. return
3. For a survey of the ways the argument is used in ethical arguments, see Wilbren van der Burg, "The Slippery Slope Argument," Ethics 102, Oct. 1991. return
4. For a discussion of some of the linguistic issues involved, see Kees van Deempter, "The Sorites Fallacy and the Context-dependence of Vague Predicates," in Kanazawa, Pinon and de Swart (eds.), Quantifiers, Deduction, and Context. CSLI Publications, Stanford. return
5. This reads as if Scalia intended to warn supporters of anti-masturbation statutes that the Texas sodomy decision puts these laws on shaky grounds. And so it does, provided, of course, that the act is consensual. return
6. "Euthanasia Legislation: A Reply to the Nonreligious Objections," in Biomedical Ethics, ed. Thomas A. Mappes and Jane S. Zembaty, McGraw-Hill, 1986. return
*(Added 7/2): The earliest citation I've found for the expression is from "An Arab Fable, " by Lydia Howard Sigourney, in Gleanings, 1860:
Once in his shop a workman wrought
With languid hand, and listless thought,
When through the open window's space
Behold!-a Camel thrust his face.
"My nose is cold," he meekly cried,
"Oh, let me warm it by thy side."
Since no denial word was said,
In came the nose,- in came the head,
As sure as sermon follows text
The long, excursive neck came next,
And then, as falls the threatening storm
In leap'd the whole ungainly form
Aghast the owner gazed around,
And on the rude invader frown'd,
Convinc'd as closer still he prest,
There was no room for such a guest,
Yet more astonish'd, heard him say,
"If incommoded, go your way,
For in this place I choose to stay."
Oh, youthful hearts, to gladness born,
Treat not this Arab lore with scorn.
To evil habit's earliest wile
Lend neither ear, nor glance, nor smile,
Choke the dark fountain ere it flows,
Nor even admit the Camel's Nose.