Irrational is the fear that impels otherwise reasonable people to shun arguments that could admit, even in the extreme, to a dreaded “slippery slope.” You know the types: The ones who invoke a rhetorically ice-strewn incline in much the same way that bomb throwers on Teh Interwebz cite Hitler as a reason that someone else is an evil idiot.

Slippery slopes aren’t inherently bad — at least, not in the non-technical sense of the phrase that most people understand. “Slippery slope” remains a loaded way of acknowledging that some arguments, primarily moral ones, almost never lead to a black-or-white conclusion; what’s “slippery” is the grey area between the moral poles. Gillikinism #1: “The rhetorical volume of one’s opinion is inversely proportional to the wisdom contained therein.” The more strident the claim to a moral absolute, or lack thereof, the less likely that the claimant understands his own argument.

But there’s a problem here.

Moral philosophy admits to several equally respectable approaches that nevertheless lead to different conclusions. A Kantian, for example, tends to favor duty over most other motivations and follows the universal maxims, like the Golden Rule, for dealing with others. Consequentialists care less about duty and more about creating the best long-term outcome for the greatest number, even if sometimes you have to crack a few eggs to get the omelet. Divine-command theorists — usually the ones who preach about God’s Will — use the Bible (or Koran) as a definitive rulebook, although it’s interesting to note in passing that relatively few ethicists accept non-religious imperatives (e.g., environmentalism or socialism or whatever) as valid sources of the “divine command” even though they should. Care ethicists strive to preserve the relationships of those involved in a dispute even if the final resolution gets creative. In all, there are roughly a dozen major ethical paradigms, each of which has a high degree of internal coherence and each of which can lead to a very different answer based on the same set of inputs.

Given this diversity of ethical opinion, some people conclude that there’s no such thing as objective moral truth. As such, a genteel pluralism ought to reign; non-judgmentalism and a well-meaning but pervasive relativism become the putative hallmarks of enlightened thought.

It’s hard to escape the relativism trap, mostly because except for the other person employing genuinely atrocious logic, the only way you can successfully fight against the ethical judgment of another is to impose your own moral framework upon his moral framework. Forcing one man’s ethical standards on another smacks of imperialism, racism, sexism, heterosexualism or whatever -ism gets your goat. To the extent that we have “shared moral values,” we’re merely acknowledging the happy accident that most ethical paradigms share certain principles. But when those principles diverge, we retreat to our own private judgments and a good relativist will refrain from arguing with the judgments of others.

Except, of course, when they won’t; it’s a hallmark of contemporary relativism that what happens in the bedroom is privileged but other things, like disbelieving in anthropogenic global warming, warrants public castigation. Ideology often trumps ethics, and the language of the ethical becomes merely a convenient weapon in what is essentially an ideological battle. Indeed, because many people don’t follow an ethical paradigm with perfect fidelity, it’s not uncommon for people to deploy duty-based principles in one context, communitarian principles in another and even to rely on religious precepts for still other contexts. When people unconsciously pick-and-choose their ethical framework depending on the circumstances of the moment, outside influences like ideology have the chance to more strongly influence the final judgment.

Relativism fails us, though, in one major respect: If we concede that what’s ethically appropriate remains in the eye of the beholder, then we cannot draw a meaningful public line over what’s permissible and what isn’t.

Contemporary debate about marriage bears this failure out. For millennia, marriage was the legal and sexual union of one man and one woman. In the late 20th century, gay-rights activists began fighting for the law to recognize marriage as including same-sex pairs. Their argument was a moral one: “Marriage equality” is a right, and people who oppose the right are homophobic bigots. And no one wants to be a bigot, right? Yet when people pushed back, public discourse slowly grow to accept the pro-gay-marriage position while castigating those who opposed it as trying to impose their religious values on gays who didn’t accept them. Which was true. And it was also true that the activists were imposting their own values on those who didn’t accept them. Two-way street.

A good relativist would say, “Well, I’m not gay and I wouldn’t marry a (wo)man, but if others really love their partners, then who am I to judge?” (Unspoken cognate: “Well, I’m gay, but I recognize that marriage has had a stable definition over thousands of years so I’ll find a way to express my love using institutions that don’t conflict with majoritarian preferences until such time that the majority sees it the same way and the transition is uncontroversial.”)

When a person retreats to relativism as a default position within a moral dispute, what we really have is moral nihilism — the denial that there’s a shared moral understanding at all, or that some judgments are intrinsically more valuable than others. Nihilism doesn’t need to be explicit to be effective; to adopt the position that we each have our private morality and there cannot be an reconciliation or accommodation without someone being the “victim” is to deny that ethics as a concept remains viable.

When the choice is between relativism or absolutism, relativism usually wins. And by extension, then, nihilism wins as well.

In complicated ethical disputes, the real virtue lies not in asserting or withdrawing an ethical perspective, but in engaging with another to reconcile the discrepancies between their value systems. In short, the only way to avoid nihilism is to embrace the slippery slope — to accept the shades of grey, and to never retreat into a world where one’s core convictions lose their force to guide action in the world.

Just be sure to put on your crampons.