The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
Being aware of the slippery slope mechanisms can help counter them: such awareness may help prevent the initial decision A that might set the slippage in motion, and may possibly stop B even if A is indeed enacted.
This awareness, of course, is part of why ideological advocacy groups, such as the ACLU and the NRA, try to persuade people to pay attention to slippery slope risks. These groups' efforts may have helped prevent us from slipping down various slopes; I've heard people who don't much agree with the ACLU express gratitude that it exists, precisely because its vigilance often helps prevent sensible regulations from leading to broader prohibitions.
Slippery slope risks thus help explain and, to some extent, justify these groups' behavior. Such groups are often faulted as being extremist or unwilling to endorse reasonable compromises; these criticisms may often be largely correct and politically potent, and may lead voters to distrust these groups. What's more, the perceived extremism of some advocacy groups can increase the public's concerns about slippery slopes that go in the opposite direction. For instance, if a gun rights group becomes known as extremist for opposing even modest gun regulations, voters might become more skeptical of modest deregulations that the group proposes, because they may reasonably fear that the group will use such compromise deregulations to push for broader deregulations in the future. But the phenomena discussed in this article might suggest that these groups' tactics could, on balance, be sound:
[1.] Most obviously, the ACLU's or the NRA's opposition to a facially modest compromise A may seem more reasonable and less fanatical given the risk that A may indeed make a broader restriction B more likely.
[2.] Of course, one can't know for sure just how likely A is to lead to B, and some might reason that in the absence of this knowledge, the advocacy group should be willing to compromise. But the plausibility of many slippery slope mechanisms suggests that such modest compromises can indeed be dangerous. If an advocacy group strongly opposes B, it can reasonably adopt a rebuttable presumption against even small changes that might help bring B about (rebuttable by evidence that A is very good on its own, or that A is highly unlikely to lead to B).
[3.] Likewise, groups may reasonably fear that their opponents' victories could create political momentum for the opponents' broader proposals, by increasing the opponents' perceived political strength. The advocacy groups might therefore reasonably adopt an ad hominem heuristic, distasteful as it may be: "Even though we might not strongly disagree with [the Religious Right/the Brady Campaign/etc.] on this particular issue, we will still oppose them here for fear that their victory today might increase their chances of winning broader restraints tomorrow."
[4.] Advocacy groups must do more than just adopt certain policy stances; they must also persuade the public to adopt those stances. But because of rational ignorance, many voters won't be willing to adopt complex, nuanced policy positions—rather, they'll need simple heuristics that they can follow.
"Pay close attention to the purported evidence underlying gun control proposals" is thus not an effective message for the NRA to send people. It is wise advice in the abstract, but most voters won't be willing to devote the time needed to follow it. "If guns are outlawed, only outlaws will have guns" may be less accurate in theory, but it's easier to apply in practice. And under conditions of bounded rationality, it makes sense for voters to adopt a simple heuristic that quickly leads them to the right result most of the time, rather than a nuanced approach that theoretically yields the right result more often but requires extended research to apply.
Of course, it would be better yet for the ACLU or the NRA if they could persuade people to follow the heuristic "On [civil liberty/gun regulation] questions, vote the way we suggest." And if the group believes that many people might adopt this heuristic, it might want to develop a reputation for being open to moderate compromises because this reputation may build public confidence in the group's advice. But if the group believes most voters are too independent to vote exactly as it recommends in each case, and instead will insist on making the decisions themselves, the group might prefer to influence those decisions by promoting a few simple heuristics.
[5.] Finally, this need to give voters some simple heuristics increases the importance of the ad hominem heuristic. Most voters have little information about the likelihood that enacting A will eventually lead to B. They don't know how the battle over A will change the power of various advocacy groups. They don't know whether other voters have multi-peaked preferences that could make A unstable. They don't know whether A's results are likely to be evaluated in a way that will make B seem appealing. But they do know that A is being backed by a group with which they disagree most of the time, and which is also committed to ultimately enacting B. In an environment of severely bounded rationality, it makes sense for voters to adopt an ad hominem heuristic, and for advocacy groups to try to instill this heuristic in voters, though the groups should recognize that stressing this approach too much might cause a backlash among voters who find such arguments unfair, offensive, or divisive.
Of course, these considerations are only a small part of how advocacy groups plan their strategy. My point here is simply that advocacy groups are an important means of fighting the slippery slope, and that in the process of fighting it, they may reasonably take positions that would have looked unreasonable had the slippery slope risk been absent. And perhaps these groups can make their positions more politically effective by explaining more explicitly why the slippery slope is a real risk.