Why does the abortion debate refuse to go away? Why, thirty years after Roe v. Wade was supposed to have settled the issue, does it remain the most politically incendiary, polarizing pressure point in U.S. electoral, judicial, and even foreign assistance politics?

Laurie Shrage joins the legions of ethicists, constitutional lawyers, and political scientists who have grappled with this question over the years. The pragmatism she brings to the effort and her candor in seeking some distance from both the right-wing (“pro-life”) and mainstream feminist (“pro-choice”) dogmas that monopolize public discourse are admirable. But Shrage’s argument mistakes symptoms for causes and leaves most of the hardest problems unsolved.

Sounding more like some of my colleagues in American politics than a philosophy professor, Shrage immediately moves the discussion to the level of political parties and opinion polls. She argues that “Republicans use the abortion issue to forge coalitions with right-wing and fundamentalist Christian voters. Democrats use it to attract women voters. Neither party will risk modifying its rigid position for fear of alienating the constituencies that the abortion issue has helped attract.” True enough, but hardly surprising. Political parties and politicians use whatever they can to win voters. Large, established organizations focused on lobbying and electoral strategies fear losing funds and adherents if they veer too far from their familiar, single-issue line. But none of this helps to explain why the abortion debate continues to define the central difference between the two major parties; or why groups such as the Christian Coalition and the National Right to Life Committee in the case of the Republicans, the Feminist Majority and NARAL in that of the Democrats, continue to win identity as the party’s “base.” What is it about the all-or-nothing approach to abortion that makes it so intractable?

Similar omissions occur in how Shrage invokes public opinion surveys. She berates both parties, and the “right-to-life” and feminist organizations they respectively try to placate, for failing to recognize the broad middle ground that public opinion data handily offers them. “[T]he majority of American voters,” according to the polls Shrage relies on, “support the right to choose in the first trimester but would like to see more restrictions on access in the second.”

In the first place, this only tells us how successful the campaign against so-called “partial birth” abortions has been in the past five years in shifting the ground of the debate (indeed, Shrage’s article itself is evidence of this success). Opinion polls prior to the late 1990s focused on “reasons” for abortion, not on gestational age. Second, such opinion poll responses are notoriously sensitive to the wording...