Before last week's South Carolina Republican debate, Ron Paul supporters complained that their candidate was not getting the first-tier attention his polling and fundraising should bring. It is true that Paul has often been overlooked and dismissed, as one might treat a slightly dotty uncle. But perhaps some first-tier scrutiny is deserved.

Paul was the only candidate at the debate to make news, calling for the repeal of laws against prostitution, cocaine and heroin. The freedom to use drugs, he argued, is equivalent to the freedom of people to “practice their religion and say their prayers.” Liberty must be defended “across the board.” “It is amazing that we want freedom to pick our future in a spiritual way,” he said, “but not when it comes to our personal habits.”

This argument is strangely framed: If you tolerate Zoroastrianism, you must be able to buy heroin at the quickie mart. But it is an authentic application of libertarianism, which reduces the whole of political philosophy to a single slogan: Do what you will — pray or inject or turn a trick — as long as no one else gets hurt.

Even by this permissive standard, drug legalization fails. The de facto decriminalization of drugs in some neighborhoods — say, in Washington, D.C. — has encouraged widespread addiction. Children, freed from the care of their addicted parents, have the liberty to play in parks decorated by used needles. Addicts are liberated into lives of prostitution and homelessness.

But Paul had an answer to this criticism. “How many people here would use heroin if it were legal? I bet nobody would,” he said to applause and laughter. Paul was claiming that good people — people like the Republicans in the room — would not abuse their freedom, unlike those others who don't deserve our sympathy.

The problem, of course, is that even people in the room may have had sons or daughters who struggled with addiction. Or maybe even have personal experience with the freedom that comes from alcohol and drug abuse. One imagines they did not laugh or cheer.

Libertarians often cover their views with a powdered wig of 18th- and 19th-century philosophy. They cite Locke, Smith and Mill as advocates of a peaceable kingdom — a utopia of cooperation and spontaneous order. But the reality of libertarianism was on display in South Carolina. Paul concluded his answer by doing a jeering rendition of an addict's voice: “Oh yeah, I need the government to take care of me. I don't want to use heroin, so I need these laws.”

This is not “The Wealth of Nations” or the “Second Treatise on Government.” It is Social Darwinism. It is the arrogance of the strong. It is contempt for the vulnerable and suffering.

The conservative alternative to libertarianism is necessarily more complex. It is the teaching of classical political philosophy and the Jewish and Christian traditions that true liberty must be appropriate to human nature. The freedom to enslave oneself with drugs is the freedom of the fish to live on land, or the freedom of birds to inhabit the ocean — which is to say, it is not freedom at all. Responsible, self-governing citizens do not grow wild like blackberries. They are cultivated in institutions — families, religious communities and decent, orderly neighborhoods. And government has a limited but important role in reinforcing social norms and expectations — including laws against drugs and against the exploitation of men and women in the sex trade.

It was just 12 years ago — though it seems like a political lifetime — that a Republican presidential candidate visited a rural drug treatment center outside Des Moines, Iowa. Moved by the stories of recovering young addicts, Texas Gov. George W. Bush talked of his own struggles with alcohol. “I'm on a walk. And it's a never-ending walk as far as I'm concerned. ... I want you to know that your life's walk is shared by a lot of other people, even some who wear suits.”

In determining who is a “major” candidate for president, let's begin here. Those who support the legalization of heroin while mocking addicts are marginal. It is difficult to be a first-tier candidate while holding second-rate values.

michaelgerson@washpost.com