Natural Law and the Antislavery Constitutional Tradition is first a work of history, highlighting the importance of natural-law thinking in nineteenth-century constitutionalism. But at the same time, it also offers a normative defense of that thinking against democratic theory and the Rawlsian tradition, both of which dismiss or deemphasize it. Which takes precedence? Justin Buckley Dyer's heart seems to lie in theory, though his strongest contributions are historical.

Natural Law and the Antislavery Constitutional Tradition makes two arguments. The first is that—notwithstanding its infamous compromises—the original U.S. Constitution was fundamentally an anti-slavery document, insofar as it institutionalizes the natural-law principles undergirding the Declaration of Independence. The second is that the Constitution ought to be interpreted in the context of what it aspires to be, which is to say an institutionalization of natural law—and that judges who ruled the right way in antebellum slavery cases adopted just such an “aspirational” approach. Neither of these arguments is new, of course: Dyer associates both with Abraham Lincoln, who slammed the Dred Scott ruling in 1857 for violating “the plain unmistakable language of the Declaration” and who famously described the Declaration's principles as the “apple of gold” for which the Constitution—the “picture of silver”—was made (p. 22).

Modern scholars, though, are not quite as sanguine about the Constitution. Rogers Smith's “multiple traditions” thesis (Civic Ideals, 1997) suggests that the Constitution embodies both pro- and anti-slavery positions, a view shared by Mark Graber in his provocative (2006) Dred Scott and the Problem of Constitutional Evil. Mark Brandon (Free in the World, 1998) goes further, arguing that the Constitution really had no teleological “aspirations” at all. And still others, following the abolitionist William Lloyd Garrison (not to mention Chief Justice Roger Taney in Dred Scott), maintain that the original Constitution was decidedly pro-slavery. Against these views, Dyer highlights a tradition connecting Lincoln with John Quincy Adams, Frederick Douglass, and Supreme Court Justice John McLean (who dissented in Dred)—all of whom held that the Constitution was essentially anti-slavery (and should be interpreted as such), insofar as it rested on a foundation of natural law.

That tradition derives, Dyer argues in Chapter 2, from Lord Chief Justice Mansfield's common-law ruling in Somerset v. Stewart (1772), which declared slavery to be “so odious [that] nothing can be suffered to support it but positive law” (quoted on p. 37). Somerset, Dyer says, enabled anti-slavery judges to appeal to the natural law when positive law was unclear. (Slavery's defenders appealed to natural law, too, Dyer notes, but such arguments were “much less prevalent in the first quarter of the nineteenth century” [p. 42].) Conversely, pro-slavery rulings—like John Marshall's in The Antelope (1825)—downplayed the importance of natural-law considerations. Marshall described Antelope as a conflict between “the sacred rights of liberty and property”—but Dyer says that that already denies the principle of natural equality by implying that certain human beings may legitimately be considered “property” (p. 63).

In Chapter 3, Dyer follows his historical thread through John Quincy Adams, who carried on the mantle of natural-law aspirationalism at a time when advocates on both sides increasingly viewed the Constitution as pro-slavery. Arguing in the Amistad case (1841), Adams characterized the existence of slavery as a matter of “fact against right”—a “constitutional disharmony,” in Dyer's words, between America as it was and America as its founding documents (including the Constitution) envisioned it (pp. 75, 77). That vision, based in the Declaration of Independence, was for Adams “both true in principle and constitutionally relevant” (p. 86). Both Lincoln and Douglass shared Adams's view—as did Justice McLean, whose Dred Scott dissent (often regarded as a mere polemic) rested on the move that Marshall did not make in Antelope: a substantive definition of “property” that excluded human beings, grounded on the Declaration's twin principles of natural equality and autonomy (pp. 125–31). Dyer's discussion of McLean in Chapter 4 is among the book's best passages; it is also strong evidence for his contention that our squeamishness about natural law has undermined our historical scholarship.

Dyer, however, also wants to make the case for natural law in itself—to borrow his line about Adams, he wants to convince us that natural law is both true in principle and constitutionally relevant—and his argument grows more theoretical (and, I think, weaker) when he turns to Lincoln and Douglass in Chapters 5 and 6. There, he pits Lincoln's and Douglass's aspirationalism against modern constitutionalists like Graber and Brandon—and especially John Rawls, with his “peculiarly modern notion of ‘public reason’” (p. 164)—all of whom eschew teleology in favor of institutions that limit power and maintain peaceful consensus among individuals with differing conceptions of the good. Lincoln, Douglass, and the aspirational tradition (and Dyer) support the Constitution insofar as they find the Declaration's natural-law principles implicit in it; Rawlsians and consensus democrats support the Constitution insofar as they believe it “cabin[s] religious and philosophical doctrines from public debate about political matters” (p. 164). It is a fascinating debate, with conundrums on all sides, but Dyer does not really engage it. He points out (correctly) that “public reason” and consensus democracy are more aligned with John Calhoun's “concurrent majorities” and the popular sovereignty of Stephen A. Douglas than with Lincoln's theological moralism, and he cites Michael Sandel's observation that Rawls “would have a hard time explaining, in 1858, why Lincoln was right and Douglas was wrong” (quoted on p. 168). But then he largely leaves it there, as if that reductio ad absurdum alone was enough to bring down Rawls and prove the case for natural law. (Graber—who concluded his own book by stumping for John Bell over Lincoln in 1860—certainly would not agree.)

I am sympathetic to Dyer's argument here—without a substantive component, Rawls and consensus democrats do have a hard time answering the prior question of who counts as a citizen of a given society—but I am still left wanting more. Dyer also raises some important problems for natural-law theory, like Oliver Wendell Holmes's point that a judge can never be sufficiently certain just what the natural law is—but he barely addresses them. Engaging those critiques is beyond the scope of a purely historical study, but it is necessary if the author wants to show that Lincoln's view is correct in itself, as well as rooted in history.

Still, Dyer's first book is a worthwhile rejoinder to the prevailing trend of histories depicting the Constitution as neutral-at-best on slavery. I am still not convinced that the trend is wrong: Dyer does show that anti-slavery, natural-law aspirationalism has “deep roots in the American political tradition” (p. 152). But Graber and Smith are not arguing that anti-slavery aspirationalism is not deeply rooted; they are arguing that pro-slavery aspirationalism is deeply rooted, too. To make the point stronger, future work beyond Natural Law will have to do more to pick apart the pro-slavery tradition; and there is also room to emphasize the anti-slavery side further. (Dyer focuses on judicial rulings, and so there is little mention here of the Constitutional ratification debate, say, or where the Framers themselves actually stood.) Alone, this book is not as persuasive as the author wants it to be, but it is nonetheless an important reminder that the natural-law tradition is not to be dismissed lightly.