That may be partly because their frame of reference is ordinary legislation in a constitutional democracy, and on that subject what they have to say is more useful. In this connection, they draw upon the ideas that John Stuart Mill developed about compromise through his experience in Parliament. In Gutmann and Thompson’s rendering, Mill believed that a compromise is “morally defensible insofar as the time is not ripe to realize the measure your own side prefers, your opponents’ position contains something worthy, the agreement would not set back progress already made, and it would facilitate future cooperation.” In addition, a “compromise should ‘embody or recognize’ the principle that you are trying to realize, even if it falls short of doing so.” The approach to compromise favored by Gutmann and Thompson calls for “principled prudence,” mutual respect, and a variety of methods for “economizing on disagreement,” such as restraining rhetoric—all reasonable and constructive ideas.

Until recently, who would have thought it necessary to offer Americans advice in the ways of compromise? We used to enjoy a reputation for being a practical-minded people, our politicians being regarded as an all-too-flexible species. But something has changed, and according to Gutmann and Thompson, the change has to do with the relation of campaigning and governing. During campaign season, they say, an “uncompromising mindset” is understandable, but it should give way to a “compromising mindset” when elections are over. But campaigning now spills into the season of governing, and the result is a persistent failure to reach agreements.

Compromise has also become more difficult because the two major political parties have become ideologically polarized. Gutmann and Thompson take no position on whether polarization affects only political elites or also the mass public, nor do they single out either party as being more responsible than the other for the trend. This is a bit too even-handed. As Jacob Hacker and Paul Pierson showed in Off Center: The Republic Revolution and the Erosion of American Democracy, polarization has been asymmetrical: Republicans in Congress have moved further to the right than Democrats have moved to the left. While the GOP has been busy removing moderates from its congressional ranks, the Democrats remain more heterogeneous. In the past decade, Congress has included more Democrats willing to compromise when Republicans are in power than Republicans willing to compromise when Democrats are in power.

The American public is asymmetrical in another respect that is relevant to the question of compromise. In late 2010 and early 2011, Gallup asked people to rate themselves on a scale of one to five, “where one means it is more important for politicians to compromise to get things done, and five means it is more important for politicians to stick to their beliefs even if little gets done.” Among those who described themselves as “very conservative,” 53 percent ranked themselves at four or five on that scale. Among the “very liberal,” only 17 percent did so. Republicans were generally more inclined than Democrats to say that it is “more important for politicians to stick to their beliefs even if little gets done.”