“Capital in the Twenty-First Century,” the new book by the French economist Thomas Piketty, is a bona fide phenomenon. Other books on economics have been best sellers, but Mr. Piketty’s contribution is serious, discourse-changing scholarship in a way most best sellers aren’t. And conservatives are terrified. Thus James Pethokoukis of the American Enterprise Institute warns in National Review that Mr. Piketty’s work must be refuted, because otherwise it “will spread among the clerisy and reshape the political economic landscape on which all future policy battles will be waged.”

Well, good luck with that. The really striking thing about the debate so far is that the right seems unable to mount any kind of substantive counterattack to Mr. Piketty’s thesis. Instead, the response has been all about name-calling — in particular, claims that Mr. Piketty is a Marxist, and so is anyone who considers inequality of income and wealth an important issue.

I’ll come back to the name-calling in a moment. First, let’s talk about why “Capital” is having such an impact.

Mr. Piketty is hardly the first economist to point out that we are experiencing a sharp rise in inequality, or even to emphasize the contrast between slow income growth for most of the population and soaring incomes at the top. It’s true that Mr. Piketty and his colleagues have added a great deal of historical depth to our knowledge, demonstrating that we really are living in a new Gilded Age. But we’ve known that for a while.

No, what’s really new about “Capital” is the way it demolishes that most cherished of conservative myths, the insistence that we’re living in a meritocracy in which great wealth is earned and deserved.

For the past couple of decades, the conservative response to attempts to make soaring incomes at the top into a political issue has involved two lines of defense: first, denial that the rich are actually doing as well and the rest as badly as they are, but when denial fails, claims that those soaring incomes at the top are a justified reward for services rendered. Don’t call them the 1 percent, or the wealthy; call them “job creators.”

But how do you make that defense if the rich derive much of their income not from the work they do but from the assets they own? And what if great wealth comes increasingly not from enterprise but from inheritance?

What Mr. Piketty shows is that these are not idle questions. Western societies before World War I were indeed dominated by an oligarchy of inherited wealth — and his book makes a compelling case that we’re well on our way back toward that state.

So what’s a conservative, fearing that this diagnosis might be used to justify higher taxes on the wealthy, to do? He could try to refute Mr. Piketty in a substantive way, but, so far, I’ve seen no sign of that happening. Instead, as I said, it has been all about name-calling.

I guess this shouldn’t be surprising. I’ve been involved in debates over inequality for more than two decades, and have yet to see conservative “experts” manage to dispute the numbers without tripping over their own intellectual shoelaces. Why, it’s almost as if the facts are fundamentally not on their side. At the same time, red-baiting anyone who questions any aspect of free-market dogma has been standard right-wing operating procedure ever since the likes of William F. Buckley tried to block the teaching of Keynesian economics, not by showing that it was wrong, but by denouncing it as “collectivist.”

Still, it has been amazing to watch conservatives, one after another, denounce Mr. Piketty as a Marxist. Even Mr. Pethokoukis, who is more sophisticated than the rest, calls “Capital” a work of “soft Marxism,” which only makes sense if the mere mention of unequal wealth makes you a Marxist. (And maybe that’s how they see it: recently former Senator Rick Santorum denounced the term “middle class” as “Marxism talk,” because, you see, we don’t have classes in America.)

And The Wall Street Journal’s review, predictably, goes the whole distance, somehow segueing from Mr. Piketty’s call for progressive taxation as a way to limit the concentration of wealth — a remedy as American as apple pie, once advocated not just by leading economists but by mainstream politicians, up to and including Teddy Roosevelt — to the evils of Stalinism. Is that really the best The Journal can do? The answer, apparently, is yes.

Now, the fact that apologists for America’s oligarchs are evidently at a loss for coherent arguments doesn’t mean that they are on the run politically. Money still talks — indeed, thanks in part to the Roberts court, it talks louder than ever. Still, ideas matter too, shaping both how we talk about society and, eventually, what we do. And the Piketty panic shows that the right has run out of ideas.