Foreign policy: Are we in or are we out?

Lawrence Kaplan has an excellent essay on the polarized ideas informing the liberal reaction to the war in Iraq, and he crystalizes the difficulty they've had in dealing with U.S. foreign policy in recent years like so:

Every time America goes to war, it unearths a contradiction at the heart of American liberalism. The contradiction pits the liberal ideal that discourages impinging on the autonomy of others against the liberal ideal that no people ought to be governed without their consent--and that liberals ought therefore to support the democratic aspirations of foreign peoples. The tension between the two manifests itself in every war, with liberals who heeded Hans Morgenthau's admonition to mind our own business arguing that we have no right to violate the sovereignty of a Yugoslavia or an Iraq, while the descendants of Woodrow Wilson argue that to do otherwise would amount to a betrayal of liberalism.

What's just as interesting is that conservatives and libertarians have a similar split, between the non-interventionist isolationism profferred by libertarian diehards and the aggressive, democracy-spreading bent of pro-war neocons. It is this debate -- on both sides of the aisle -- that will inform the future of American policy, with Iraq as the test case. How it will play out will largely depend on whether or not Iraq is seen as a failure (looking more possible every day), and if so, if it's a failure that can be modified into a success or a failure that can be best learned from by avoiding it in the future.