The Volokh Conspiracy

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Slippery Slope Arguments

Slippery Slope June: Eleven General Thoughts About Slippery Slope Arguments


[This month, I'm serializing my 2003 Harvard Law Review article, The Mechanisms of the Slippery Slope; in yesterday's post, I laid out some examples and definitions, but here I want to flag several observations.]

[1.] Though the metaphor of the slippery slope suggests that there's one fundamental mechanism through which the slippage happens, there are actually many different ways that decision A can make decision B more likely. Many of these ways have little to do with the mechanisms that people often think of when they hear the phrase "slippery slope": development by analogy, by changes in people's moral or empirical attitudes, or by "desensitization" of people to earlier decisions.

[2.] As the gun registration/confiscation example in yesterday's post illustrates, slippery slopes are not limited to judicial-judicial ones, where one judicial decision leads to another through the force of judicial precedent. They can also be legislative-legislative, where one legislative decision leads to another (Madison's concern in his famous Remonstrance Against Religious Assessments), judicial-legislative, or legislative-judicial.

[3.] Slippery slopes may occur even when a principled distinction can be drawn between decisions A and B. The question shouldn't be "Can we draw the line between A and B?," but rather "Is it likely that other citizens, judges, and legislators will draw the line there?"

More broadly, the question ought not be "How should society (or the legal system) decide whether to implement A?" Societies are composed of people who have different views, so one person or group of people may want to oppose A for fear of what others will do if A is accepted. And these others need not constitute a majority of society: slippery slopes can happen even if A will lead only a significant minority of voters to support B, if that minority is the swing vote.

[4.] In a stylized world where voters and legislators are fully rational, have unlimited time to invest in political decisions, and have single-peaked preferences (more on this in a later post), slippery slopes are unlikely. In such a world, if B is unpopular today, it will still be unpopular tomorrow, whether or not A is enacted; enacting A therefore won't cause any slippage to B. The skepticism about slippery slopes may come partly from the common tendency to assume that we are living in this stylized world, an assumption that is often a sensible first-order approximation.

It turns out, though, that the mechanisms of many slippery slopes are closely connected to phenomena that contradict these simplifying assumptions: bounded rationality, rational ignorance, heuristics that people develop to deal with their bounded rationality, irrational choice behaviors such as context-dependence, and multi-peaked preferences. And because these phenomena are common in the real world of voters, legislators, and judges, slippery slopes are more likely than one might at first think.

[5.] Slippery slopes are also connected to path dependence. Once law B has been enacted, it's often easy to assume that its enactment was predetermined by powerful social forces that no one could have derailed. But the path dependence literature suggests that sometimes a decision A can shift the evolution of a legal rule from one course to another, bringing about a B that would not have otherwise happened. The study of slippery slopes can thus illuminate forms of path dependence that haven't yet been fully investigated, and the study of path dependence can help illuminate the slippery slope phenomenon.

[6.] One kind of slippery slope—the attitude-altering slippery slope—is connected to expressive theories of law. The law, these theories suggest, "affects behavior … by what it says rather than by what it does"; a classic example is laws against smoking in public places strengthening a no-smoking-in-public-places norm even when those laws are rarely enforced. Attitude-altering slippery slopes happen when the expressive power of law changes people's political behavior as well as their other behavior, by leading them to accept proposals that they would have rejected before.

[7.] The existence of the slippery slope creates what I call the slippery slope inefficiency: decision A might itself be socially beneficial, and many people might agree that it's beneficial; but some swing voters' concern that A will lead to B might prevent decision A from being implemented. One corollary of the inquiry "How likely is A to lead to B?" is the inquiry "How can we make it less likely that A will lead to B, so that we can reach agreement on A despite some people's concern about B?" I propose a few hypotheses along these lines.

First, substantive constitutional limits on government power can be regulation-enabling, not just regulation-frustrating. A non-absolute constitutional right to get an abortion, to speak, or to own guns can free people to vote for small burdens on the right with less concern that these small steps will lead to broader constraints.

Second, constitutional equality rights—under the Equal Protection Clause, the Free Speech Clause, or other provisions—are themselves means by which decision A may lead to decision B, because a court might conclude that implementing A without implementing B would violate the equality rule. {Of course, this slippage will happen only if the court concludes that A and B are similar enough along some relevant metric; and by hypothesis, the person deciding whether to support A despite the risk that it will lead to B thinks that A and B are quite different—A being good and B being bad. But there's nothing inconsistent here: one might see A and B as materially different, but might fear that a court applying the equality rule will disagree.} Deferential equality tests, such as the current weak rational basis test that applies to many equal protection claims, can thus prevent this type of slippery slope.

Third, legislators may sometimes decrease the risk of certain kinds of slippery slopes—such as political momentum slippery slopes—by enacting proposal A as part of a compromise where each side gets some change in the current policy, so that neither side is seen as the clear winner.

[8.] Recognizing slippery slope concerns might lead us to modify the rules of thumb we use for evaluating the potential downstream effects of proposals. For example, people often urge others not to make a big deal out of small burdens: if a new proposal seems to have low costs (to liberty or the public fisc), it should be supported, or at least not strongly opposed, even if its likely benefits are low. Many say this about modest restrictions on privacy, gun ownership, abortion, and other behavior—the restrictions may not offer huge benefits, but neither do they seriously restrict rights, so why not try them? Maybe the experiment will pleasantly surprise us, or give us some helpful information about which proposals work and which don't. And beyond this, fighting a modest experiment might make us seem foolishly intransigent—an argument often levied against abortion rights or gun rights "extremists."

But the more we believe that one step now may lead to other steps later, the more we may view such experimentation with concern. We might therefore adopt a rebuttable presumption against even small changes, under which we oppose any proposal A (in certain areas) unless we see it as having great benefits, because even a seemingly modest restriction has the added cost of increasing the chances of undesirable broader restrictions B in the future. And this concern, if it can be persuasively articulated, can provide a response to the "You're an extremist" argument.

Likewise, we are often cautioned against ad hominem arguments and against impugning our political opponents' motives, and there is much to these cautions. Nonetheless, the existence of some slippery slope mechanisms suggests that what one might call an ad hominem heuristic—a policy of presumptively opposing even minor proposals made by certain groups that also support broader proposals, unless the proposals clearly seem to be very good indeed—may be more pragmatically rational than one might think.

[9.] These heuristics may also shed light on the behavior of advocacy groups such as the ACLU or the NRA. Public consciousness of the possibility of slippage may help prevent the slippage, either by preventing the first steps or by building opposition to the subsequent ones. One role of advocacy groups is to alert the public to slippery slope risks, partly by trying to instill the heuristics mentioned above. This strategy can be dangerous for advocacy groups because it may make them seem extremist. But, as I discuss throughout and summarize in section VII.B, real slippery slope risks may make such a strategy necessary.

[10.] Thinking about legislative slippery slopes illuminates two aspects of judicial decisionmaking: reliance on precedent (where judicial-judicial slippery slopes may appear) and deference to the legislature (where legislative-judicial slippery slopes may operate). These parts of the judicial process, it turns out, are closely connected to analogous processes in legislative decisionmaking.

[11.] Thus, slippery slopes present a real risk—not always, but often enough that we cannot lightly ignore the possibility of such slippage. "In the absence of absolute knowledge and consequently absolute control over the consequences of our actions and decisions, we cannot afford to ignore the possible misuses of proposed reforms."

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Coming posts in this series explore the different kinds of slippery slopes that I have identified, illustrating each with a variety of hypotheticals based on real controversies. I hope that readers will find at least some of these illustrations plausible, and will conclude that slippery slopes are possible (even if not certain) in some of these situations.