Henry Farrell has started an interesting blogosphere discussion of 'left neoliberalism' and about a 'theory of politics. The post has provoked responses from Delong. Cosma Shalizi's take on the whole thing is worth a read:
What Henry means when he talks about “a theory of politics” is a theory about how political change (or stasis) happens, not about what political ends are desirable, or just, or legitimate, which is much of what I take “political theory” to be. “What are the processes and mechanisms by which political change happens?” is, at least in part, a separate question from “What would a good polity look like?”, and Henry is talking about the former, not the latter. Of course the answer to the first question will tend to be context-dependent, so specialize it to “in contemporary representative democracies”, or even “America today” if you like.
The first importance of such a theory is instrumental: if you want to have policies that look like X, a good theory of politics would help you figure out how to achieve X-shaped policies. But the second importance is that the theory might change your evaluation of policies, because it would change your understanding of their effects. The U.S. tax deduction for mortgage interest is arguably economically inefficient, since it promotes buying housing over renting, for no very clear economic rationale. But in so doing it (along with massive government intervention in forming and sustaining the mortgage market, building roads, using zoning to limit the construction of rental property, etc.) helps create a large group of people who are, or think of themselves as, property owners, possessors of substantial capital assets and so with a stake in the system*. If the deduction were, for instance, means-tested, it would not be nearly so effective politically.
Or again, if, for instance, you like material prosperity, you might favor policy X because (you think) it promotes economic efficiency. (Some other time, we can and should have the conversation about “economic efficiency”, and the difference between “allocating scarce resources to their most valuable uses” and “allocating resources to meet effective demand”, i.e., about the injustice inherent in the market's social welfare function.) But if you are also egalitarian, and policy X would make it easier for a small group of already-privileged people to wield political influence, then you might decide that policy X is not, after all, worth it, because of its inegalitarian political effects. (At a guess, some, but not all**, of Brad DeLong's reaction to Henry's posts is explained by letting X = “Clinton-era financial deregulation”.) If you value a certain kind of distribution of political power as such (democracy, aristocracy, the vanguard party, rule by philosopher kings central bankers, etc.), a theory of politics would becomes an important part of how you gauge the value of different policies, at least ones which you think would tend to change how much power different individuals, or groups of individuals, would have.