Some time ago, I heard a power company executive arguing that humans have played no role in global warming. Actually, he went further, “demonstrating” that global warming isn’t even happening. (This is often done by cherry-picking dates to start with an unusually warm year.) He ended by spreading his arms and beseeching us in his common-sense voice, “Can’t we meet in the sensible middle?”

To which I thought, “If I say the moon is made of lunar rock and you say it is made of green cheese, is the ‘sensible middle’ that the moon is half lunar rock and half green cheese?”

That’s the problem with sensible middles. You can’t do the give-and-take without agreeing on facts. Nowadays, some of the thorniest problems get hung up on one side’s dismissal (or corruption) of accepted science. We can compromise over how far our society will go in confronting climate change, but we must first agree it exists.

Thus, when we ask questions like “Would Hillary Clinton be a centrist president?” what do we mean by that? We can be sure that if nominated, Clinton the candidate will try to seem centrist, as will her Republican foe. Americans like the sound of moderation.

Some debates can’t logically end in compromise. The right to abortion does not lend itself to concessions, making it a land mine for Republicans in a general election. Religious conservatives want abortion banned, but most Americans want it kept legal. So you have Republican candidates saying that they oppose abortion but would allow it in cases of rape and incest.

They may even paint others as extremist: “My opponent won’t even make an exception for rape or incest.”

In reality, the so-called extreme position is the only logical “pro-life” stance. If one holds that the organism formed at conception is a full human person, it is a full human being whether conceived through rape or through marital love. There is no biological difference.

I don’t agree that two cells fused at fertilization are a full human being. I respect the views of those who do, but not if they won’t accept the consequences of their position.

Another problem in reaching a sensible middle is finding the middle. Tax and spending policy is an area where compromise can be reached. But there’s no middle to work toward when one side portrays any tax increase as a deal killer.

In 2011, eight Republicans running for president were asked at a debate whether they’d accept a deal with Democrats giving them $10 in spending cuts for every $1 in tax increases. This would seem a conservative’s debt reduction dream, but not one of the eight would say yes to it.

The candidates were surely mindful of President George H.W. Bush’s electoral loss after breaking his pledge, “Read my lips: No new taxes.” The elder Bush happened to be doing the responsible thing, but his party’s right wing had moved fiscal management from the realm of political science to black-and-white religion.

Today this faction doesn’t want its leaders to be seen shaking hands with President Obama, much less compromising with him on matters of substance. The outcome is Republicans disinheriting their own ideas because Obama has adopted them. The great example was the Affordable Care Act, whose blueprint came out of the conservative Heritage Foundation.

Many Americans only pretend to seek a sensible middle by placing the middle in the middle of their stuck beliefs. No, it’s worse than that. Many are scuttling rational thought altogether, accepting or rejecting beliefs not on their merits but based on who is holding them. The end product is neither a middle nor sensible.

Email Froma Harrop at fharrop@gmail.com.