President Obama is said to have made the case for a liberal public policy agenda in his State of the Union speech the other night. But what is liberalism?

The conventional view is that liberalism is an ideology. In fact it is a sociology.

An ideology is a set of ideas that cohere. Socialism is an ideology. So is libertarianism. Suppose I told you that socialists believe the government should nationalize the steel industry and the auto industry. You would have no difficulty inferring what their position is on nationalizing the airline industry. Right? Suppose I told you that libertarians believe in a free market for tinker toys and ham sandwiches. You would have no difficulty inferring that they also believe in a free market for Rubik’s Cubes.

Sociologies are different. They represent a set of ideas that are often incoherent. These ideas are likely to come together not because of reason, but because of history or happenstance. Not only do the ideas not cohere, they may be completely contradictory.

Take the issue of preschool education – forcefully endorsed by the president the other night. As David Brooks explained, the issue is really about allowing poor children to escape from the anti-education atmosphere of their homes to a place that will at least give them a chance to learn. Given a person’s position on preschool education for four year olds, shouldn’t you be able to predict how he will think about allowing poor six- and seven-year-old children to escape from bad schools? As it turns out you can’t.

Brooks explains the preschool issue this way:

This is rude to say, but here’s what this is about: Millions of parents don’t have the means, the skill or, in some cases, the interest in building their children’s future. Early childhood education is about building structures so both parents and children learn practical life skills. It’s about getting kids from disorganized homes into rooms with kids from organized homes so good habits will rub off. It’s about instilling achievement values where they are absent.

Okay, so how is that different from the situation faced by slightly older children trapped in lousy schools where teachers couldn’t care less what they learn? It isn’t. Yet so many of those who favor preschool education (a new and expensive entitlement) are reliable opponents of vouchers, charter schools, firing bad teachers, closing bad schools or any other remedy that offends the teacher’s unions. And that includes President Obama.

Then there is the issue of the minimum wage. The minimum wage does almost nothing to relieve poverty. That’s because almost no one who is a head of household is earning the minimum wage for any length of time. However, I think it is fairly well-established that a higher minimum wage gives teenagers in above-average income households more pocket change, even as it closes off job opportunities for poor, minority teenagers. (Remember, the black teenage unemployment rate is about twice that of whites.) If you want to maximize job opportunities for low-income youngsters, as President Obama says he does, you certainly wouldn’t want a minimum wage standing between a minority youth and his first job. Yet creating that barrier and making it permanent is part of the Obama agenda for the labor market.

A related issue is public policy toward unions. There is no mystery about what a union is. It is an attempt to monopolize the supply of labor to employers. In most all cases, unions confer special (monopoly) status on workers who are solidly middle class, allowing them to seek above-market wages by closing off competition from those who earn less and have less. Yet encouraging labor unions is another core pillar of the Obama presidency.

Finally, our federal deficit is almost totally caused by entitlement spending on the elderly. Our government routinely sends Social Security checks to billionaires and pays their medical bills to boot – paid for in part by a 15.3% payroll tax imposed on the parents of the children to whom the president would like to provide preschool education.

The zip codes in America where people cash the largest Social Security checks are the very same zip codes where Medicare spends the most dollars on the average enrollee. And unlike the income tax, every worker pays the payroll tax – no matter how poor. Yet these are the programs that President Obama resists reforming.

Some readers will be quick to point out that the Democratic Party – dating back to the days of Franklin Roosevelt – consists of a coalition of interests and that winning elections requires satisfying each of those interests. Fair enough. But we are here talking about thinking, not winning elections.

Politicians will invariably search for some intellectual justification for what they do. Since their policies are incoherent, no ideology will serve their purpose. What they need is a sociology – a way of thinking about the world that defends the indefensible. They need intellectuals who will apologize for the mixed economy welfare state without any obvious sense of embarrassment. For the Obama administration, that sociology is liberalism. Its adherents once called themselves “liberals.” Today, they are “progressives.”