The lines of debate—vigorous debate—about the nation's wars have in recent months increasingly cut across party lines, in a refreshing dilution of the lockstep partisanship that so often characterizes what passes for debate on important issues of public policy in the United States. The cross-cutting lines have become apparent on Afghanistan as Republican impatience has been catching up with Democratic discontent over the war. Last month an amendment sponsored by Democrat James McGovern and Republican Walter Jones and calling for an accelerated withdrawal of troops from Afghanistan attracted votes from 26 House Republicans as well as a majority of House Democrats. Then there are comments from Republican presidential candidates, including front-runner Mitt Romney, about the need to bring U.S. troops home soon. The 2008 Republican standard-bearer, John McCain, who favors staying the course in Afghanistan, has been expressing as much consternation about pro-withdrawal sentiment in his own party as about such sentiment among Democrats.

Now, regarding another war under debate, McCain has joined with Democrat John Kerry to introduce a resolution authorizing limited use of U.S. military forces in Libya. The Kerry-McCain resolution would fill the gap left by the Obama administration's contorted position that U.S. involvement in the war doesn't really constitute involvement in a war. The resolution also is intended to ward off legislation being prepared by another bipartisan alliance—Democrat Dennis Kucinich and Republicans Joe Heck and Justin Amash—that would cut off funds for military operations in Libya.

Regardless of what anyone thinks about the wars in question, all this cross-aisle positioning is a good thing. The more that legislators, and their constituents, are forced to get away from the lazy habit of forming opinions and beliefs on the basis of party identification (a habit that is a major source of mistaken beliefs) rather than identifying with a party on the basis of well-formed opinions and well-grounded beliefs, the better off the republic will be. Without clear party-line cues to follow, more people are forced to do more serious thinking for themselves on these issues.

The cross-cutting lines of contention on these wars is even better than the broad-consensus, politics-stops-at-the-water's-edge kind of bipartisanship that has been seen at times in the past. A largely unchallenged consensus has underlain some of the nation's biggest foreign policy failures. A consensus about the nature of international communism that led the United States into the Vietnam War is probably still the outstanding example.

Of course, partisan maneuvering is not absent from the current war debates. Some Republicans are expressing skepticism about current policies at least partly to make trouble for Barack Obama, and some Democrats are defending current policies at least partly out of loyalty to their party's president. But at least party loyalists have to contend with opposing arguments coming from inside as well as outside their own party.

It also is a good thing for some Republicans and some Democrats to favor the same course of action for different reasons, as is true with some of the cross-aisle alliances on the wars. The more different reasons that are openly discussed, the better the chance of identifying the best reasons, and the better the chance that the marketplace of ideas will sort out good reasons from the bad ones.