On MSNBC last night, Chris Hayes quoted White House press secretary Robert Gibbs:

There are no more arbiters of truth. So whatever you can prove factually, somebody else can find something else and point to it with enough ferocity to get people to believe it. We’ve crossed some Rubicon into the unknown.

Great quote–but why have we crossed “some Rubicon”? Last night on the air, Jonathan Kay attributed it to the Internet echo chamber effect: People are selecting their information sources based on what they believe, then getting their beliefs reaffirmed, etc. Politico makes the same attribution–following, in turn, the logic of the White House itself (as quoted in the Politico story).

This explanation is not sufficient, I say.

First, there’s been a trend over 40 years to create conservative think tanks that put out their own version of reality and their own version of expertise–so that now, “for every Ph.D. there’s an equal and opposite Ph.D.,” to quote Andy Revkin from somewhere or other. Meanwhile, Fox News has a stronger effect on unreal perceptions than blogs, I would say, and it is “old media.”

In fact, media balancing itself creates a more postmodern culture, as we know from the research. And again, we’re talking about old media, not new.

So the question is much more complicated, and you can’t just blame the Internet. What do others think? Are there other factors I’ve neglected?