In a romantic mood, I was reading “Anna Karenina” flying down here and stumbled across one of Tolstoy’s brilliant insights.

At a party at the home of his friend Prince Oblonsky, Konstantin Levin, the philosophical farmer, muses about the futility of dinnertable debates.

Tolstoy writes: “Levin had often noticed in discussions between the most intelligent people that after enormous efforts, and the enormous expenditures of logical subtleties and words, the disputants finally came to be aware that what they had so long been struggling to prove to one another had long ago, from the beginning of the argument, been known to both, but that they liked different things.”

This is the way I feel about the debate over Social Security. Forget about the projections of fiscal calamity or paradise. We have known from the beginning of the argument the central fact: the two sides like different things.

One side likes the government to take care of people, whether they need it or not. The other side — which I’m on — likes people to make their own choices and take responsibility for their own lives.

The first side sees Social Security as “social insurance” — the most persistent vestige of the collectivist approach to solving public-policy problems. The other side sees freedom as the route to personal and national prosperity.

Just as we buy our own food, clothes and shelter, we should put away a little bit at each pay period for our retirement. Yes, we need to take care of people who can’t earn enough to build a nest egg. But, for the vast majority of Americans, saving for retirement over 40 years isn’t particularly difficult or risky. It’s a lot safer than going deeply into debt to buy a house — which two-thirds of families do.

Each side marshals the numbers to prove it’s right, but numbers really aren’t the point. This is a clash between two starkly different visions — between people who like different things. The best way to change what people like is not through math but through chemistry — that is, through appeals to ideals and ideas.

But, just as the Bush Administration failed — until the president’s 2005 inaugural address — to make the right case for the war in Iraq, it is failing to make the right case for Social Security reform. On Iraq, America went to the U.N. with legalisms instead of principle, a vision of democracy as a force that makes the world more safe. Social Security reform, similarly, is rooted in the principle that personal liberty is a force that makes America richer and more secure.

In both cases, the simple truth is that we like freedom and responsibility while the other side likes collectivism and intervention.

There’s no doubt that the left understands what’s at stake. In a roundtable on the future of the Democratic Party, Michael Tomasky, executive editor of The American Prospect, was asked Sunday by the New York Times, “Is there some meeting ground?”

“Not on Social Security,” he said. “As a principle Social Security is inviolate.”

Why? First, because it is all that remains of the New Deal, the shards of a sinking ship to which Democrats believe they must cling. Second, because, if personal accounts are realized, the proportion of Americans with a stake in the stock market will rise from half to about four-fifths. And when people own stocks, they become friendlier to free markets and more inimical to government interference.

Aspiring nations have already caught on. In a speech March 2 at the American Enterprise Institute’s annual dinner, the Peruvian novelist and political theorist Mario Vargas Llosa pointed out that in Latin America, 11 countries have reformed their creaky pension systems with personal accounts in recent years — “whereas the more backward left in the United States opposes the privatization of Social Security.”

Why so retrograde? Because the institutions with power on the left — not the Democratic Party but labor unions, the press, the AARP, academe and anti-globalizers — don’t want change. Their nightmare is union members with large-cap mutual funds, seniors who don’t rely on checks from the U.S. Treasury.

This is not the time for the Administration and congressional Republicans to go wobbly on Social Security. Instead, in this contest over likes, not numbers, it’s time to take the gloves off and start slugging it out over principle.