I wonder how Dick Durbin and Saxby Chambliss plan on convincing the House of Representatives to vote for tax increases as part of their deficit reduction plan. I mean, it’s nice that Chamblss (and apparently Tom Coburn and Mike Crapo, too) realizes that that they have to give on taxes in return for compromises on entitlements, but, unless I’m wrong, nearly every Republican in Congress has signed a pledge at some point not to raise taxes. For those Republicans for whom this isn’t an article of faith, there is still the matter of keeping their word.

The Gang of Six has been meeting at Sen. Mark Warner’s Northern Virginia home (which I envision as quite luxurious) for months now. The group, which also includes retiring Senate Budget Chairman Kent Conrad of North Dakota, has been trying to hammer out an agreement that can actually pass through Congress. Evidently, the three Republicans long ago conceded that any deal must include cuts in defense spending and higher taxes or it would have no chance of winning Democratic votes.

On the Democratic side, they conceded that cuts in the growth of Medicare and Medicaid will be necessary. But they’ve conceded, as well, that Social Security must get some kind of haircut or the deal won’t attract any Republicans. This is, of course, kind of obvious to any casual observer. But what’s not clear is that the Republicans would vote for higher taxes even in return for the elimination of Social Security and Medicare. They are so in the grip of their ideology that I don’t know how they can be enticed to break out. As for the Democrats, they will not touch Social Security unless there is a hell of deal dangling on the line. I don’t see the Republicans baiting their hook with “a hell of a deal.”

In theory, the three conservative Republican members of the Gang of Six could lend some political cover and even some credibility to any grand deal. I guess Dick Durbin is supposed to provide the same service on the other side of the aisle.

But I don’t see it happening.

An administration official recalled that in early 2010, when Mr. Durbin was named to Mr. Obama’s fiscal commission, another White House official told its co-chairmen, “You’ll never get Durbin’s vote.”

Nine months later, Mr. Durbin announced his support in The Chicago Tribune for the recommendations the chairmen had negotiated with members. “The question my closest political friends are asking is this: Why is a progressive like Dick Durbin voting for this deficit commission report?” he wrote. The answer: “Borrowing 40 cents out of every dollar we spend for missiles or food stamps is unsustainable.”

So, Mr. Durbin added, “when we engage in the critical decisions about our nation’s future budgets, I want progressive voices at the table to argue that we must protect the most vulnerable in our society and demand fairness in budget cuts.”

That has been his mantra with disappointed allies in labor, women’s groups and the Senate. Mr. Durbin, in the interview, cited a private meeting requested by Senator Bernie Sanders, independent of Vermont, a socialist and “a good friend.” Their exchange, Mr. Durbin said, captured the increasing difficulty in being a good progressive “at a time of limited resources.”

Mr. Sanders said he respected Mr. Durbin for his good intentions. “But I think the direction in which he is going in working with some of the most very conservative members of the Senate is not correct,” Mr. Sanders said.

Increasingly, it doesn’t appear that the two parties are operating in worlds that share the same physical properties. If we can’t agree that carbon in the atmosphere causes dangerous climate change, or that the study of biology is predicated on evolution, or that the study of geology is predicated on plate tectonics, then how can we agree that the Sun sets in the West, let alone on something as massive as a bill that cuts entitlements and raises taxes?

I think that is Bernie Sanders’s point. And, even though the New York Times twice reminds us that Bernie is a Socialist, he’s really just a progressive, like many other Democrats, especially in the House. I know I’d be willing to listen to a proposal. I just can’t imagine a proposal that would be acceptable to Tom Coburn being acceptable to me. That kind of compromise probably doesn’t exist.