Why Liberals and Conservatives Clash offers an explanation for the extreme polarization between liberal and conservative that is the hallmark of the American political landscape today. It suggests that liberal thought is intrinsically different from conservative thought, and that each constitutes a self-subsistent world-view with its specific qualities and rules. The book offers a set of guidelines to predict a person's views based on other views s/he holds, given that each world-view is what it is for structural reasons, and is more than merely a sum of discrete positions. It explains, for example, why people who support gay marriage also typically support the woman's right to an early-term abortion, and why people who demand that citizens "support the military" understand this as meaning, support putting members of the military in harm's way. Because liberal thought and conservative thought each constitutes a closed world-view, neither side will ever convince the other in an argument. The most we can hope for is an acknowledgment by each side of the usefulness of the other, a goal Fleming proposes as the most reasonable one for our times.

Why Liberals and Conservatives Clash makes logical the most striking, and hitherto puzzling feature of the contemporary American political landscape: its acrimony, its air of being an argument between the deaf: neither side understands the other. Fleming suggests this is so because neither side accepts the bases underlying the other's particular positions. We can, however, understand that they are different, and that trying to force the other side into submission won't work. We need to go beyond liberals dismissing conservatives with horror and conservatives dismissing liberals with disgust. Conservatives aren't merely imperfect liberals, they're something else entirely. Liberals aren't merely potential conservatives, they actually think differently.