But equally obviously, they are not the whole of politics nor anywhere near it. Policy is not made, in the US or anywhere else, through value-neutral debate among technocrats about the relative efficiency of different proposed schemes. Hence, the need for a theory of politics – that is, a theory of how policy proposals can be guided through the political process, and implemented without being completely undermined. And this is all the more important, because (on most plausible theories of politics) there are interaction effects between policy choices at time a and politics at time a+1. The policy choices you make now may have broad political consequences in the future. Obvious examples include policies on campaign spending, or union organization, which directly affect the ability of political actors to mobilize in the future.
This remains a debate on policy implementation taking place within a narrow band of acceptable political opinion, with the difference between Yglesias and Farrell being that the first is a policy wonk, the latter more of a politics wonk, but neither seems comfortable contronting the more fundamental question of ideology, nor are the commenters.