Rather than extracting a paragraph from this New York Times piece about gay marriage by the American conservative thinker David Blankenhorn, I urge you to read the whole thing. In it, he explains that after long opposition to gay marriage, he has come round to supporting it, albeit with caveats. In the acrimonious stand-off that American politics has become, such side-switching is very unusual. You don't have to agree with every point Blankenhorn makes - or indeed any - to admire the clarity of his prose, and, above all, the spirit in which he writes.
There's hardly anything I respect more than someone struggling honestly to come to terms with a way of seeing the world that is very different from their own. The volte-face achieved through the hard work of reason is very rare indeed. We all pretend to be open to different points of view. But in reality, most of us stick to a narrow spectrum of opinions shared by our friends and peers, one which yokes different issues together simply because they're part of the same cultural gestalt (there's no fundamental reason that being pro-European should align with being pro-choice, for instance, or indeed - to take two more obviously related issues - to oppose abortion and support the death penalty).
We also tend to stick doggedly to our own view, come what may. While pretending to be open to evidence, we will go to amazing lengths to fit new evidence to pre-existing beliefs, rather than the other way around. I stopped taking Tony Blair's antagonists in the media seriously (well OK, perhaps I never did) after seeing them build Lord Hutton up as an incorruptible man of granite who would finally impale that slippery Blair on the rusty sword of truth - and then, following the publication of his report, which inconveniently exonerated Blair and his government from any wrongdoing, immediately denounce him as an establishment dupe. Blair's donation of his entire book proceeds to charity somehow reinforced rather than undermined the view of the same people that the former PM was money-grabbing and cynical.
A more general example is the response of avid pro-Europeans - including Blair, incidentally - to the Eurozone crisis. Rather than conceding that their consistent advocacy of Britain's entry to the Eurozone would have led to disaster, and that the Eurosceptics were right to warn of its inherent instability, Blair, Heseltine, Clegg and others have been blithely pretending that the current crisis is just a spot of bother, a mere diversion from the great river of European integration. It doesn't appear to have occurred to them to ask themselves whether and why they got things so wrong.
People change their mind for social reasons - when their peers and wider social group do so - or for political reasons: when it might benefit them to do so. The rarity of honestly reasoned changes of mind appears to support a slightly depressing idea recently proposed by French social scientists, called the "argumentative theory of reasoning". The gist of it is that reason and rationality evolved not to serve truth, but to win arguments. We are wired to care much more about being on the right side of an argument - and being seen to be on the right side - than about being right. In the words of one of the theory's authors, reason is "a purely social phenomenon. It evolved to help us convince others and to be careful when others try to convince us.”
Of course, even if reason evolved for that purpose, that doesn't mean we have to use it that way. David Blankenhorn's article is a small reminder of the higher purposes to which our capacities for self-reflection and hard thinking can be put.