In the Shadow of Leviathan is a worthy sequel to Jeffrey Collins's outstanding 2005 book, The Allegiance of Thomas Hobbes. In his new book, Collins returns to Hobbes, but his focus has shifted to Hobbes's influence in the years after the publication of the English version of Leviathan. Collins is especially interested in Hobbes's influence on Locke, and his book, as the subtitle indicates, is ultimately more about Locke than about Hobbes. Collins tells the story of Locke's early immersion in Hobbes's writings and his acceptance of Hobbes's outlook followed by his gradual departure from Hobbes on the question of religious toleration. It would be too simple to say that Collins's Locke moved, as others would have it, from a Hobbesian opposition to toleration to a protoliberal defense of it, for Collins's Hobbes was more open to toleration, under certain circumstances, than is often thought. According to Collins, rather, Locke departed from Hobbes by moving from a politique understanding of toleration, as granted at the discretion of the sovereign, to a principled defense of toleration as a just demand rooted in a natural right and as a limit on the authority of the sovereign.

Among the many virtues of Collins's book, the most impressive is his meticulous examination of the historical context in which the shift in Locke's thinking occurred. In a time in which many academic books are written too hastily, it is satisfying to read a work that is clearly the product of many years of painstaking research. Political theorists, in particular, will find that they have much to learn—as this one did—from Collins's thorough examination of the debates and political dynamics of the Interregnum and especially the Restoration. Collins is a historian, and so it is no surprise that he is a deeply committed contextualist. He may or may not regard himself as a member of the Cambridge School. But whether he does or not, he is trying to correct what he sees as a mistake some in that school have made in downplaying Locke's engagement with Hobbes and Hobbes's influence on him. It could seem—at times, it does seem—that Collins is moving from a Cambridge conception of Locke to a Straussian one, since Straussians, beginning with Strauss himself, tend to emphasize the connections between Hobbes and Locke. But Collins would not accept that characterization of his work, and not only for the methodological reason that he works by means of political contextualization much more than most Straussians do. A more substantive difference is his greater emphasis on questions of conscience rights and religious toleration; and a still more fundamental one is that Collins's Locke is more pious than Strauss's.

If political theorists will learn much from Collins about historical matters such as the twists and turns of the battles over the Stuart Indulgences, they may grow weary of following Collins down so many byways as he discusses yet another set of secondary figures, chasing rabbits into the brush of history. As is so often the case with scholarship, the great virtue of Collins's work, its meticulous examination of the historical record, becomes at times its vice, since the voluminous discussion of secondary figures makes Collins's text tedious in stretches and distracts from his main line of argument. More important, Collins's approach comes at a substantive cost. One will find in his book an exceptionally thorough analysis of the political dynamics that surrounded Locke's pivot toward a more principled defense of religious toleration. What one will not find is a detailed examination of Locke's views as they are revealed in his most important texts. For instance, Collins notes that it is hard to reconcile Locke's epistemological skepticism with his appeal to natural law (180–81, 257). But Collins does not dig very deeply into the questions of which of these was more fundamental for Locke and which played a more decisive role in his embrace of toleration. It is striking that Collins does not discuss works such as Adam Wolfson's Persecution or Toleration, Steven Forde's Locke, Science, and Politics, and J. Judd Owens's Making Religion Safe for Democracy, in which these questions are discussed at length. To be sure, Collins's own answers to the questions are clear enough: Locke's commitment to natural law was fundamental and provided the bedrock of his concern for a principled form of toleration (see, e.g., 241, 256–57, 270, 371). But these answers are not defended adequately against the main alternatives, which are dismissed as untenable without much further argument (see, e.g., 117, 257, 327–29, 341–44). These alternative readings of Locke are not only Straussian readings, because, as Collins himself stresses, many of Locke's contemporaries thought his skepticism was deeper than his commitment to a robust form of natural law, which they regarded as disingenuous (see, e.g., 327–31, 350–52). How can we be sure that they were wrong, given Locke's willingness—which Collins himself acknowledges—to dissemble regarding important matters, including the depth of his engagement with Hobbes?

It seems to me that Collins does not provide a sufficient answer to this last question. As a result, his account of the movement in Locke's thinking about toleration does a better job, in my view, of answering some questions than it does of answering others. Collins is at his best when he is explaining the complicated political dynamics that surrounded Locke's change of heart and in some respects caused it, as Locke came to see that the Hobbesian approach of leaving toleration to the discretion of the sovereign was proving to be an inadequate guarantee of conscience rights and religious liberty in both England and France. The reader is thus given an extremely detailed account of when Locke's view changed and some account of why it did. But the account of the why is incomplete, since political dynamics alone, as Collins acknowledges (see, e.g., 180–81, 262–63, 271, 371–72, 376), provide only a partial explanation. Locke's reaction to those dynamics surely depended on their interaction with his core convictions, since someone with other core convictions—say, more Hobbesian ones—might well not have worried much about the inadequacy of prerogative indulgence to secure religious liberty. Thus, it makes a crucial difference what Locke's core convictions were. But that, to repeat, is a question that I do not think Collins adequately answers, not because he does not give an answer, but because he does not defend the answer he gives with a sufficiently detailed account of the most important texts, including Locke's Epistola de Tolerantia and his far more extensive Essay concerning Human Understanding.