One of the great advantages of blogging is that reading a debate online can be a far more clarifying and informative way to understand the world than absorbing one long article or a book. It's just the way we're wired. We can be engaged in conversation more easily than being forced to concentrate on a monologue alone. All of which is a roundabout way of saying: read Manzi on McArdle on Yglesias. Serious blog-power on one of most fascinating policy conundrums we have.