Most of the talk generated by Tuesday’s Democratic debate is about e-mails or enemies, but far more important were the efforts of the presidential candidates to explain what they would do about achieving another e-word: equality.

And when they spoke of inequality, it was clear that their concern was the accumulation of wealth and power by the very wealthy.

Inequality is on everybody’s lips these days. But what if everybody’s wrong? That’s the contention of “On Inequality,” a small, smart new volume by Princeton University philosopher Harry Frankfurt.

His simple but powerful thesis: “Our most fundamental challenge is not the fact that the incomes of Americans are widely unequal. It is, rather, the fact that too many of our people are poor.”

Progressives, in other words, are shooting at the wrong target. The moral problem posed by the distribution of wealth isn’t inequality.

It’s poverty.

The same issue? Frankfurt shows they’re not. Suppose, he says, there is a resource that will keep a person alive, but only if that person has five units of it. There are 10 people, and 40 units of the resource. If it’s distributed equally, everybody gets four units — and dies. To insist on equality in that case, he argues, “would be morally grotesque.”

Fortunately, says Frankfurt, we don’t really try to promote equality. Even those who worry about inequality adjust their consumption to their own assessments of their needs. They don’t reduce their consumption because it’s unfair for them to have money.

This instinct he lauds: “A preoccupation with the condition of others . . . leads a person away from understanding what he himself truly requires in order effectively to pursue his own most authentic needs, interests, and ambitions.”

Frankfurt suggests that the instinct that leads many to complain about inequality isn’t about equality at all: Their objection “is not that some of the individuals in those circumstances have less money than others. Rather, it is the fact that those with less have too little.”

He’s on strong ground here. There is a tendency on the left to think of inequality principally as a problem of the rich having too much. Frankfurt contends that this worry is a distraction from the far more important goal of making sure everyone has enough.

My progressive friends who bemoan inequality usually define the problem not as the poor having too little but as the rich having too much. I was raised to the liberalism of the 1960s, when assisting those worst off was first priority.

Think the problems are the same? Just glance at the income curve and cut off the very tip of the right tail — that is, eliminate the superrich. The shape of the curve doesn’t change. The poor are just as poor as they were before.

One reason for the obsession with curbing the power of wealth is a concern that the rich can buy more political influence than they deserve. My worry is that what’s really going on isn’t a struggle over the outsize influence of the very rich, but a struggle over who should exercise outsize influence.

After all, the beneficiaries of a taming of the influence of the rich would be not the poor and downtrodden but the educated professional classes who have long dominated the academy and the news media.

Frankfurt warns us not to measure our circumstances against those of others: “If a person has enough resources to provide for the satisfaction of his needs and interests, his resources are then entirely adequate; their adequacy does not depend in addition on the magnitude of the resources other people possess.”

What people deserve equally, Frankfurt contends, is not equality in money but equality in respect. This might require making sure that everyone has a particular amount of a particular good, but it doesn’t require making sure that everyone has the same amount of that good.

An example is health care. We might agree everyone has the right to a particular standard of care without decreeing that everyone must be able to buy what the rich can. Frankfurt presumably would come down in the first camp: that you can buy more health care than I is morally irrelevant as long as I can buy enough.

Before you cringe in horror, bear in mind that the Affordable Care Act is structured exactly on this model, and that even Sen. Bernie Sanders, in Tuesday’s debate, referred to people’s right to “the health care that they need” — not the health care that they want.

Frankfurt’s short book (89 pages) should be required reading for candidates of both parties, if only to get them to focus on his central point: For all our fine talk about inequality, what’s truly terrible in America is not that so few have so much. It’s that so many have so little.

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