The mother of all problems in higher education today is high tuition at public colleges and universities, which forces students into decades of debt and makes for-profit schools seem like a plausible alternative.

College used to be free at institutions like the University of California and other state schools not that long ago. In 2014, tuition was abolished in, of all places, Tennessee. And in January, Obama asked Congress to fund a plan making two-year community colleges tuition-free. That’s a good start, but we need more. Making four years of college free is not only fair; it’s also politically possible.

The University of California provides an example of the problem. In 2014, in-state tuition and fees for undergrads totaled $13,222 for one year. And UC isn’t even the most expensive public university: in-state tuition for the current school year at Penn State is $18,464. (The cheapest is the University of Wyoming, at $4,646 for one year.) As a result, two-thirds of college seniors now graduate with an average of $29,000 in student-loan debt. Students are told that incurring this debt is justifiable because a college education increases their earning power and boosts their “human capital”—which, they are told, is a financial advantage that goes beyond net worth. As Forbes explained it, student debt will provide “a solid return on your investment.”

That rationale suggests the ubiquity of market logic today. But there’s an alternative way of thinking: education is a public good. The purpose of education is not just to enable people to increase their lifetime incomes; it’s to help them understand the world, to stimulate the imagination and inspire creativity in all fields. A good society provides opportunities for everyone. We need educated people. And we should be willing to pay to educate them.

Why is tuition so high? The original sin of today’s public university systems can be found in the withering-away of state funding. This is a recent phenomenon: in Ronald Reagan’s campaign to become governor of California in 1966, he ran against the university, but he didn’t raise the tuition after he won. When Reagan left office in 1975, UC tuition cost only $647. It skyrocketed after 1990: $2,700 in 2000, $5,400 in 2005, almost $10,000 in 2010. In California, Democrats won a supermajority in the state legislature in 2012, which let them accomplish political tasks once considered impossible (for example, making abortion more accessible), and last year voters turned drug possession from a felony to a misdemeanor. But there have been no cuts in tuition; the Democrats agreed only to freeze the increases—and now they’ve declared that the freeze is coming to an end. In response, the UC Board of Regents recently voted to increase tuition by 5 percent per year for the next five years. For residents, the tuition would go from $12,192 now to $15,564.

There’s a simple, elegant solution to this travesty: tuition at public colleges should be free. You may say that’s impossible, but, as noted, it was free in California and other states just fifty years ago. You may say that was then, this is now. But college is free now in Sweden, Denmark and Finland, while in France, public universities are free for students from lower-income families, and those from higher-income families pay about $200 a year. You may say none of these countries provide a good model for the United States, and that once tuition goes up, it never comes back down. But what about Germany? It introduced tuition eight years ago, but over the last eight years, every state in Germany has abolished it.

How they did it provides a model for the United States, and it can be summed up in three words: protest and politics. Some preliminary facts: Germany has the fourth-largest economy in the world. Public higher education there is controlled and funded by sixteen autonomous state governments rather than the federal government. Following the American example, those state governments imposed tuition starting in 2005. But German citizens organized the Alliance Against Tuition Fees, which included not just student unions but trade unions and political parties. Students marched in the streets all over the country after the first seven states introduced fees. In Hamburg, they organized a fee strike; in the state of Hesse, which includes Frankfurt, they occupied the universities, and 70,000 people signed a petition in support. The Christian Democratic government in Hesse, facing an election in 2008, reversed course and promised to eliminate tuition. “Those state governments that followed Hesse’s lead in abolishing fees stayed in power,” Times Higher Education reported; “those that refused were removed from office at the next election.” Even in conservative Bavaria, 1.35 million voters—15 percent of the electorate—signed a petition opposing tuition, causing the state government to relent. If the conservative Christian Democrats in Germany—masters of austerity—can be pressured into eliminating tuition, why can’t the same thing happen with the Democrats in the United States, especially in places like California, Illinois and New York?

The US government already spends lots of money on student aid. Federal spending in 2014, the College Board reports, includes $47 billion in grants, $101 billion in loans and $20 billion in tax credits. “With that kind of dough,” says Anya Kamenetz of NPR, “there ought to be ways of buying better access and more equity.” One prominent proposal, from the Campaign for Free College Tuition, calls for offering a full college scholarship to every academically qualified student whose family makes less than $160,000 a year ($160,000 because even the middle class has gone into debt paying for college). Instead of federal Pell Grants and tuition tax credits, we’d create an entitlement: all young people who qualify for college can go for free.

Obama’s plan doesn’t go that far: he proposes that the federal government pay three-quarters of the cost of tuition for two-year public community colleges, and that states pay the rest. Students would have to be enrolled at least half-time, maintain a C-plus average, and “make steady progress toward completing a program.” If all fifty states agreed to fund the program, it could cover 9 million students and save each one about $3,800 a year. Republicans, of course, are not going to fund such an initiative, leading one GOP spokesman to label Obama’s proposal “more of a talking point than a plan.”

A little arithmetic suggests that the proposal would cost the federal government something like $25 billion a year, while the states would have to come up with another $6 billion. ...