The Mechanisms of the Slippery Slope

You are a legislator, a voter, a judge, a commentator, or an advocacy group leader. You need to decide whether to endorse decision A, for instance a partial-birth abortion ban, a limited school choice program, or a gun registration mandate. You think A might be a fairly good idea on its own, or at least not a very bad one. But you're afraid that A might eventually lead other legislators, voters, or judges to implement policy B, which you strongly oppose—for instance, broader abortion restrictions, an extensive school choice program, or a total gun ban. What does make sense for you to do, given your opposition to B, and given your awareness that others in society might not share your views? Should you heed James Madison's admonition that it is proper to take alarm at the first experiment on our liberties, and oppose a decision that you might have otherwise supported were not for your concern about the slippery slope? Or should you accept the immediate benefits of A, and trust that even after A is enacted, B will be avoided? Slippery slopes are, I will argue, a real cause for concern, as legal thinkers such as President James Madison, Justice Robert Jackson, Justice William Brennan, Justice John Harlan, and Justice Hugo Black have recognized, and as our own experience at least partly bears out: can all identify situations where one group's support of a first step A eventually made easier for others to implement a step B that might not have happened without A (though may disagree about exactly which situations exhibit this quality). Such an A may not have logically required the corresponding B, yet for political and psychological reasons, helped bring B about. But, as thinkers such as President Abraham Lincoln, Justice Oliver Wendell Holmes, and Justice Felix Frankfurter have recognized, slippery slope objections can't always be dispositive. We accept, because must, some speech restrictions, searches and seizures, and other regulations. Each first step involves risk, but is often a risk that need to take. This need makes many people impatient with slippery slope arguments. The slippery slope argument, opponents suggest, is the claim that we ought not make a sound decision today, for fear of having to draw a sound distinction tomorrow. Exactly why, for instance, would accepting (for instance) a restriction on hate sooner or later lead to restrictions on cherish? If the legal system is willing to protect the ideas cherish today, why won't still protect them tomorrow, even if ban some other ideas in the meantime? And even if one thinks slippery slopes are possible, what about cases where the slope seems slippery both ways—where both alternative decisions might lead to bad consequences? My aim here is to analyze how can sensibly evaluate the risk of slippery slopes, a topic that has been surprisingly underinvestigated. I think the most useful definition of a slippery slope is one that covers all situations where decision A, which you might find appealing, ends up materially increasing the probability that others will bring about decision B, which you oppose.