Recent years have seen a proliferation of works examining the relationship between the liberalism for which John Stuart Mill is rightly celebrated and the imperialism for which he is equally rightly (to a degree – more on that below) condemned. Critics of liberal imperialism such as Jennifer Pitts, Uday Singh Mehta, Thomas McCarthy and Bhikhu Parekh (alongside many others) have explored the historical, personal and conceptual entanglements of Mill's philosophical commitments and his work as a colonial administrator with the East India Company (despite his own dismissive view of it, in his autobiography, as little more than a day job). These efforts have developed a considerably more complex view of Mill's political thought by expanding beyond the well-worn focus on domestic concerns (liberty, representative government, suffrage, and so on) for which he is better known. They have also contributed to a growing scholarship assessing the impact of imperialism on political theory, which, as Jennifer Pitts has noted, has been sorely neglected in the discipline.

These reasons alone would have made Georgios Varouxakis's Liberty Abroad: J. S. Mill on International Relations – the first systematic, book-length treatment of Mill's international thought – a timely and important contribution to the literature on Mill, and more broadly, on global intellectual history. But still more impressively, Liberty Abroad does what a truly successful scholarly work ought to: it shows us a Mill that we simply didn't know before. In spite of its advances, the preponderance of the literature on Mill's liberal imperialism has also obscured his abiding interests in (and nuanced treatments of) a broad range of subjects that we now lump together under the rubric of international relations. Varouxakis's accomplishment is to show us this Mill, who wrote on, thought about, and even threw himself into international politics, who cared passionately about such far-flung causes as the American Civil War and abolitionism, who helped to develop the nascent field of nineteenth-century international law, and whose public pronouncements on treaty obligations found him lambasted in London's daily newspapers. Rather than rehashing the book's arguments, I will proceed by outlining its central contributions to the scholarship on Mill's political thought, as well as a few minor reservations regarding its approach.

Liberty Abroad provides an important corrective to many of the interpretive deficits and pitfalls that recur across much of the literature on Mill's international thought. First, Mill's role as an imperialist casts a very long shadow over scholarly treatments of his writings on global politics; while this critical scrutiny is well warranted, it has also eclipsed the considerable attention that he devoted to international law (treated in chapter 2), international treaty obligations (chapter 3), non-intervention and third-party international intervention (chapter 4), and war and maritime law (chapter 6). The book's primary contribution, then, is to both draw together and carefully document Mill's surprisingly expansive – and wholly under-examined – engagements with these subjects.

But beyond neglecting these particular areas, much of the commentary on Mill's international thought, Varouxakis rightly notes, both ‘attach[es] undue weight to isolated remarks and statements, without a grasp of the full context in which they belong’ (p. 3) and ‘indulge[s] in highly anachronistic misreadings of what Mill said and wrote’ (p. 8). Liberty Abroad avoids these perils by reading Mill extensively, carefully and – most importantly – contextually; as Varouxakis notes, the ‘historical approach is the book's major distinctive feature’ (p. 3). Varouxakis's contextualism both averts the ‘mythology of doctrines’ against which Quentin Skinner cautions us and informs his reconstruction of Mill's views on international affairs, otherwise lost behind the din of empire. Drawing extensively on archival and newspaper sources, Mill's correspondence, and his impressive grasp of Mill's voluminous written corpus, Varouxakis carefully tracks the development of Mill's views on both domestic and international affairs. This is, at points, contextualism at its best: Varouxakis's meticulous documentation of Mill's efforts to sway British policy-makers in favour of the American Union (pp. 26–40), for example, ably shows the intimate relationship between his principled interests in international law and the more immediate political contexts that animated them.

Varouxakis's detailed contextualism also reveals the substantial interplay of domestic and international concerns in Mill's political thought. Far from paying a merely cursory attention to global politics, Mill was persistently preoccupied by the international sphere's entwinement with Britain's politics (the price, one supposes, of governing a global empire) and driven to exercise what influence he held over them both. His involvement with the Trent and Alabama controversies, Varouxakis shows (on pp. 26–43), reflected not only his interests in international law and the American Civil War (though they reflected those too), but also his desire to warm British public opinion to the North's cause. We here see the intersection of Mill's acuity as an international observer, his astuteness as an influential member of Britain's political elite, and the force of his moral convictions regarding the depravities of slavery. His views on international treaty obligations (detailed on pp. 44–76) comprise a similar concatenation of moral principle (on the injustice of treaty obligations understood to bind in perpetuity), international crisis (Russia's repudiation of the Treaty of Paris of 1856) and domestic policy (a clamour for war against Russia). This kind of close contextualism uncovers the imbrications of Mill's political and philosophical commitments, of his principled and pragmatic concerns, and of domestic and international spheres in his political activism. The global context was no mere afterthought in Mill's political vision, nor was it reducible to imperial anxieties; Mill's ‘strong and sustained interest in international politics and morality’ (p. 186), Varouxakis persuasively demonstrates, was an integral facet of his political philosophy.

Liberty Abroad also recovers Mill's little-documented but profound preoccupation with the American Civil War, and with the moral imperative underlying it – namely, the struggle over the abolition of slavery. Two of the book's six substantive chapters (chapters 2 and 6) detail his many points of engagement with the war, and more particularly, his conviction of its moral worth – or rather, of its moral necessity. Mill was neither a pacific idealist nor a warmonger; he maintained, with considerable force and perspicacity, that some wars, such as the American one – ‘war[s] of principle and for justice’ (p. 155) – had to be fought on moral grounds. That Mill declaimed against Carlyle's racist polemic in Fraser's Magazine is well known; that he crusaded in favour of the North and went to great lengths to galvanize the (contested) support of Britain's public and political classes shows the depth of his conviction in the war's moral rectitude.

And yet, for all of its strengths, Liberty Abroad's resolute contextualism is not without its costs. Varouxakis's wariness of ‘falling into the trap of trying to “find” Mill's doctrines or theory on the “mandatory themes” of international relations theory’ (p. 18) pushes too far in the other direction by refusing any attempt to identify principles – or, it would seem, any sense of coherence at all – guiding Mill's thoughts on international relations. What we’re left with is a fragmentary series of vignettes on seemingly disparate subjects, sparked by equally disparate events, that the author resists connecting to one another (or to any broader political philosophy) for fear of imputing an unjustified consistency to them. ‘If Mill had no clear-cut or one-size-fits-all recommendations for intervention or other international questions’, Varouxakis avers, ‘it may be better simply to say so and reconstruct as faithfully as the historical record allows what positions he did take at various stages in his life’ (185). And this is precisely what Liberty Abroad can feel like at points: a reconstruction of a few isolated crises, each so immediately bound to Mill's domestic, international and personal concerns that we would be unwarranted in extrapolating their relation to any grander philosophical commitments.

If this is the case, why bother reading Mill at all? We are invested in his opinions on international affairs precisely because of ‘Mill's status as an iconic liberal’ (p. 2), a status earned on the back of a robust philosophical vision which spoke to innumerable features of the human condition. For all of the inconsistencies pervading his expansive body of work, Mill was a system-thinker who saw important connections binding the moral, political, economic and sociological facets of human life. While he held no fixed policy of international politics to speak of, Mill did formulate distinctive moral and political doctrines, and those doctrines are precisely why we read his views, rather than any number of others’. Varouxakis's steadfast reluctance to connect Mill's thoughts on global conflicts in America, Europe and beyond to any larger political theory leaves the reader wondering why, in the end, we ought to be concerned with them. If there is no doctrine, if Mill's views comprise little more than his immediate responses to the events within which he happened to be immersed, if all that we are excavating is – to paraphrase Jeremy Waldron – ‘what Mill would allow’, then why should we care about his international thought at all? Varouxakis's methodological concerns risk pushing Mill's thoughts on international politics so far away from the philosophical doctrines that animate our interest in him that we lose track of why we should read them altogether. We have come to inhabit, as Waldron puts it, ‘an age of exquisite hermeneutic sensitivity’; while that sensitivity has undoubtedly steered us clear of any number of anachronisms, it also courts the danger, in Liberty Abroad, of obviating the very point of reading Mill's international thought.

A secondary – and minor – quibble pertains to the book's concentration on Mill's later (largely post-1848) thoughts on international politics. Varouxakis explicitly sets his sights on the ‘unmistakeable increase of focus during the last two decades of his life related to particular international events’ (p. 5), which he covers with great lucidity and precision. But, with the exception of chapter 5's treatment of empire, Liberty Abroad has little to say on the pre-1848 Mill. While this certainly is justifiable – no book can be all things – it strikes me as something of a lost opportunity, in light of the important shifts in Mill's intellectual trajectory from youth into maturity. Given his considerable growth as a thinker, it would have been fascinating, from the perspective of an intellectual history, to witness the development of his ideas on international politics. Varouxakis's compelling accounts of Mill's embroilments with the Civil War might, for instance, have been further enriched by tracing their roots in his writings on American democracy and politics from the 1830s and 1840s. On page 89, Varouxakis makes a passing reference to the foundations of Mill's later thoughts on foreign intervention in his writings from the 1830s; a more elaborate treatment might well have illustrated the genesis of his considered thoughts on the subject.

Finally, chapter 5 (on empire) falls somewhat flat by sidestepping the critique of Mill's liberal imperialism – ultimately, the most trenchant criticism of his international thought. Varouxakis has written on the subject elsewhere, as have others; and yet, Liberty Abroad pointedly avoids the best-developed expositions elaborated by such theorists as Pitts and Mehta. The chapter largely recapitulates Mill’s, his critics’ and his defenders’ rather well-known positions, but does little to address the central critical argument – that Mill's liberalism is pervaded by a stage-based account of progress that relegates non-Europeans to, as Dipesh Chakrabarty puts it, a permanent state of ‘not yet’ – beyond observing that ‘Mill was in advance of the mental habits of his time’ (p. 142). Given the force and prevalence of the critique in much of the scholarship on Mill's international thought, the somewhat tepid response makes for a notable absence.

But these are, ultimately, minor concerns with an excellent, meticulous, timely and important book. Liberty Abroad is, without a doubt, the authoritative account of Mill's international thought, and as such, is a very welcome addition to the scholarship on him.