That means that the intellectual vigor of an ideological community has a lot to do with its standards of membership. Before a community can deliberate collectively, its members have to reach a collective decision about what commitments of principle and moral reflexes entitle one to a seat at the table at which its collective deliberation occurs. When the criteria of admission are too lax, the cacophony of conflicting intellectual and moral sensibilities makes collective deliberation impossible. So a community firing on all cylinders as an engine of collective deliberation has to be prepared to excommunicate sufficiently wayward members. But when the criteria of membership are too strict, the community lacks sufficient intellectual diversity to test its principles and its reflexes against each other. To the extent that mild heterodoxy makes a member a candidate for excommunication, an ideological community’s core commitments tend to degenerate into hollow dogmas.
When you see what liberals are starting to say about each other you have to wonder whether the excommunicators are getting carried away. Here, for example, is Paul Krugman venting about Obama (my emphasis):
Notice that Krugman isn’t just saying that Obama needs to be disabused of some mistaken inferences he’s drawn from facts recognized across the liberal community. He’s saying that the president inhabits an intellectual universe in which he’s unable to distinguish hard facts from the fanciful myths that cloud the minds of movement conservatives. That sounds a lot more like an article of excommunication being prepared for submission to an inquisitorial tribunal than an invitation for a debate among liberals.“More and more, it’s becoming clear that progressives who had their hearts set on Obama were engaged in a huge act of self-delusion. Once you got past the soaring rhetoric you noticed, if you actually paid attention to what he said, that he largely accepted the conservative storyline, a view of the world, including a mythological history, that bears little resemblance to the facts.
“And confronted with a situation utterly at odds with that storyline … he stayed with the myth.”
I don’t want to overreact. Practicing politicians, especially those that have to govern, always disappoint their ideological comrades one way or another. (I remember conservatives saying that Reagan had become Gorbachev’s “useful idiot”.) Yet it’s one thing for ideologues to hold their president’s feet to the fire, another thing entirely for them to stop thinking of him as their president.