It’s a sign of the high caliber of debate within today’s Democratic Party that the 2020 presidential primary now features competing plans for student debt relief from Sens. Elizabeth Warren (D-Mass.) and Bernie Sanders (I-Vt.). Both are ambitious efforts to mend a frightening rent in the American social fabric, but they reflect a subtle and deepening divide between the two candidates on major policy problems.

The central point of both plans is the same: All tuition and fees at public universities and colleges will be eliminated. In the future, both candidates imagine, the primary driver of student debt ― expensive college education ― won’t exist.

But the plans diverge in how they deal with the $1.6 trillion in debt Americans have already accumulated.

The Sanders plan is simple: Cancel all of it, end of story.

The problem with this approach is that lots of rich people have a lot of student debt. The largest student debt balances, in general, are owed by people who end up earning the most money. So, in addition to helping the poor and the middle class, Sanders’ plan would help a good chunk of rich people, too ― including the millionaire hedge fund manager who took out loans to pay the $144,000 tuition for his Harvard MBA.

Warren’s plan tries to avoid this mess by scaling the amount of debt relief to a debtor’s income after they leave school. If your household earns up to $100,000 a year, you’ll be eligible for $50,000 in student debt relief. Households that bring in between $100,000 and $250,000 will be eligible for lower levels of relief, and those taking home $250,000 a year or more won’t get any relief at all.

Warren says her plan will result in complete debt cancellation for 75% of existing borrowers, while only the richest 5% of households would be completely excluded. But given the realities of 21st century tuition costs, even this program seems a little stingy.

Forty years ago, a prestigious state university like Virginia’s William and Mary cost in-state residents $2,962 a year for tuition and room and board. Adjusted for inflation, that’s $10,168 in today’s money. But the in-state cost for William and Mary is $36,554 next year ― meaning freshmen are looking at close to $150,00 for a four-year degree.

A lot of William and Mary grads will go on to have fabulous careers making gobs of money. But there are plenty of great, important careers out there that won’t make you rich. If this William and Mary grad moves to Washington, D.C., for a job as a social worker, he can expect to make about $50,000 a year. As a public school teacher, about $60,000. It’s easy to imagine this grad racking up six figures in debt and being stuck with a massive tab even after getting a $50,000 write-off from Warren.

There is nothing particularly radical about writing off debt. From ancient Mesopotamia and the Code of Hammurabi to modern bankruptcy courts and bank bailouts, governments have been wiping out debts for as long as the concept of credit has existed. Die-hard capitalists have their debts expunged all the time. Why not students?