My thanks to Bill, TPM, and all the book club contributors and readers this week. This weekend, share a copy of Bill's book with your favorite political opponent. It's readable, funny, and enlightening, and you will feel smarter, not angrier.

Bill's last post is a great summary. You can make a strong case that sorting has coincided with much growing inability to resolve conflict in the political culture.

Does it follow that consensus, especially a national consensus, has become harder to achieve because of sorting? I'm not yet convinced. Consensus is hard to achieve, with or without sorting. Here are three problems I would need to address, before I would argue that sorting is one of the causes.

* Sorting is an artifact of prosperity and greater choice. You may dislike the uneven distribution of these things, or the resource demands they impose. But it's reasonable to think that if the country were poorer, sorting wouldn't be as great, and if that's true, I doubt most people want that trade-off. Suppose sorting were somehow constrained, by economics or anything else. Are the prospects for national consensus enhanced? I don't see it.

Here's one test: in college campuses, are the physically proximate communities on the left and the right successfully persuading each other and synthesizing their ideas? My observation has been: not so much.

* Sorting is not motivated by political preference, even if the political consequences are serious. Both Walker and Rich touched on this point, but I would take it a step further.

Unless there is a network to support them, or unless the stakes are visible and significant, most people aren't going to risk their important personal relationships or disrupt the arc of their lives for the sake of political expression or participation. In my experience, anyway. The price that most people are willing to pay to publicize their political identity or to spice up political discourse is not very high.

* Does a political culture with more deliberation, and more ideologically diverse personal networks, really set the table for more consensus? You can find reasons to be suspicious. Read the examples in Bill's book that describe experiments where deliberation can actually harden and polarize individual opinions. Diana Mutz's Hearing the Other Side provides some detailed and sobering evidence about how deliberation can inhibit political participation and vice versa.

In the end, I think of sorting is a process and an outcome we should learn to measure and learn to manage.

Is there anything to be done? As I wrote in the first post, if you are serious about strategies to persuade your most distant ideological opponents, warm up to the task with Chapter 7 in The Big Sort.

Two final comments:

1. Isn't sorting at the local level different from sorting between states or regions? I think we need to be clear about which levels of aggregation matter, and why. Colorado (yet another great example from the book) illustrates this. You may know that Colorado is a competitive state this year in the Presidential race, and has elected both Democrats and Republicans at the statewide level recently. But Colorado is also the home of Ward Churchill and James Dobson, both reasonably insulated within Boulder and Colorado Springs respectively.

So, is Colorado homogeneous or heterogeneous? I think the answer depends on the way you decide to aggregate.

2. A quick, inadequate, take on the question: why would we think sorting is a new problem in relation to the country's entire history? Here's the take: the metrics of political sorting these days may be consistent with the historical norm, and the decades after World War II may be unusual. This claim was part of a critique of Bill's and Bob Cushing's original work on the subject by political scientist Philip Klinkner.

But is any comparison between the present and the years before World War II really meaningful? Think about the advance of communication networks, the rise of foreign policy on the national agenda, the integration of the economy, and the doubling of the country's population since the 1930's. To my thinking, the rise in sorting in recent decades is more important and more revealing than it's possible reversion to an old historical norm.