In the old (old!) movie "The Princess Bride," the heroine, in a case of mistaken identity, pushes her true love down a hill. Realizing her error, she heaves herself after him. They bounce and tumble, tumble and roll, unable to overpower momentum-- the slippery slope, if you will.

But the hill has a bottom, as every hill does, and when they reach it, they slide to a stop, wheeze a bit, gaze into each other's eyes and declare an undying love. After surmounting several dozen further obstacles, Wesley and Princess Buttercup live happily ever after.

It's a classic fairy tale, and as such has a hopelessly optimistic ending, but it does have an application in real life?

Slippery-slope arguments, never far afield, have been popping up with some frequency in recent discourse. If Obamacare's individual coverage mandate is approved, intones one, what's to stop the government from making any demand of citizens for some perceived benefit?

(Perhaps we all might be compelled to chew on raw garlic, in order to ward off bacteria and other evildoers, and to create jobs in agriculture for hardworking illegal immigrants.)

States another: If President Obama's Department of Health and Human Services can require religion-based health providers that receive government grant money to provide certain family-planning services in opposition to the better angels of their nature, what's to prevent some future administration from, say, requiring a vendor of vegan foodstuffs to sell meat (or receive government grants)?

And -- stop me if you've heard this one -- if two men or two women are allowed to marry, what's to thwart a matrimonial arrangement among seven women and five men, or three men and a cat? (Personality differences, I presume. Garlic could work, too.)

Actually, the thing that would stop most of these things from happening (much) is that they're preposterous. Rhetoric, when convenient, carries ideas to their logical extreme, wherever that may lead.

Real life -- which is mostly inconvenient -- has practical limits that kick in before that point. Locating these limits is the ongoing business of society.

When one stands at what one perceives to be a precipice, it's natural to shy away. In that case, one should remember that even a slippery slope has a stopping point.

On the other hand, those eager to take leaps of faith in the hope of banishing pain from the human condition should ponder the following line from the movie, spoken just before our protagonists are pitched down the hill:

"Life is pain, Highness. Anyone who says differently is selling something."

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David Banks is the Star Tribune's assistant commentary editor.