As a Posnerist, I am very sympathetic to the following:
For myself, I would be happy to see conservatism exit from the political scene—provided it takes liberalism with it. I would like to see us enter a post-ideological era in which policies are based on pragmatic considerations rather than on conformity to a set of preconceptions rooted in a rapidly vanishing past. We have accumulated a substantial history of liberal and conservative failures.
But there is a difference between rational preconceptions, based on theory and experience, and rigid emotional preconceptions, such as dogmatic libertarianism or egalitarianism or ungrounded hopeful beliefs such as that everybody in the world is yearning for and ready for democracy, that tell one more about the thinker’s personality than about the quality of his thought and that may be impervious to reconsideration in the light of new evidence. We should be skeptical of world views rooted in emotion that insulate people against inquiry into the foundations of their beliefs. Concretely, there is a range of perfectly respectable economic theorizing, at one end (the interventionist) typified by Paul Samuelson and at the other end (the libertarian) by Milton Friedman, but it would be a mistake to commit to one or the other end since neither can be proved to be correct.
At its best, I think conservatism is Posnerism — a skeptical but mildly meliorist approach that draws on insights from market liberalism, inherited tradition, etc. As the gap between conservatism and Posnerism has grown, conservatism has been the worse for it.