I first met Kei Hiruta in Oxford in the autumn of 2009. We were both doctoral students at the time. I was affiliated to the University of Tokyo and Hiruta Wolfson College, Oxford, the sanctuary for Isaiah Berlin. After meeting near Blackwell's bookshop, we had lunch with our mutual friend in the café of the University Church of St Mary the Virgin. I do not remember the details of the conversation as it was more than a decade ago, but I do remember that during an after-lunch walk we talked a little about what intellectual history was. In retrospect, this was the starting point for us to chat about the nature of this academic field, especially its method and methodology, when we met in person afterwards: in Cambridge, Shibuya (in Tokyo) and elsewhere. However, I never realized at the time, in Oxford in 2009, that our paths would cross in this manner and that I would be given the privilege of organizing a review forum for his awe-inspiring first book and writing this introduction.

This forum is an outgrowth of the online (Zoom) review session for Hiruta's Hannah Arendt and Isaiah Berlin (Reference Hiruta2021), hosted by the Institute for Advanced Global Studies, the University of Tokyo, Komaba, on 11 June 2022. Given that Hiruta participated in the review session across the time zone from Aarhus, Denmark, where the university he then belonged to is located, this final product is in some ways an outcome of the technological skills we have – unexpectedly though perhaps fortunately – been forced to acquire because of the contemporary pandemic. The online session was attended by more than 40 people, who listened as Hiruta first explained why he adopted the eclectic method of combining historical and politico-philosophical approaches to analyse the work of the two protagonists in comparison, before presenting the main thrusts of his book. His introduction was followed by comments from Nobutaka Otobe, Akio Futai and Ryuichi Yamaoka, who are also the contributors to this forum, and a Q&A section with the audience.

There are two twists to the present forum. First, while the above review session was conducted entirely in Japanese, this forum, as its offshoot, is in English. Second, the outlet is the Japanese Journal of Political Science, which mainly deals with Japanese politics and those of neighbouring countries, and only marginally with Western political thought. However, all of us – Hiruta, the contributors and I – believe that publishing the English reviews of Hannah Arendt and Isaiah Berlin in this journal has a symbolic and substantive meaning. In Japan, the study of both Arendt and Berlin is popular and has a rich and vibrant tradition. The bulk of their works have been the subject of translation into Japanese. Yamaoka, one of the contributors to the present forum, is also among those academics who have offered penetrating critiques of Berlin's thought in this country, thus helping to create a transnational intellectual field where the important concepts of this Oxford philosopher can serve as a shared point of reference for scholarly and heuristic dialogue across states.Footnote ¹ In short, research on the two Western thinkers is a non-negligible part of Japanese political studies, if not of mundane political phenomena here, and given Hiruta's educational background, he is at once a partial inheritor of such a local scholarship.Footnote ² Therefore, it is worth featuring his book and its reviews in the political studies journal with a Japanese rubric, despite the Western origins of its object of inquiry. Moreover, as he notes in his reply, the scholarly world of political thought in this country has a distinctive nature – ‘the fertility of Japan's untamed academia’ resulting from the flexible exchange between the sub-disciplines (see Hiruta's reply). Nevertheless, all this is generally invisible because of the language barrier. The following three English reviews can be a small window for academics outside Japan to look at the vigorous interest in Arendt and Berlin in such characteristic Japanese academia. It is here that the present forum stands out the most from the other reviews, which number more than 20! and are mostly published in Anglophone and European countries.

Meticulously researched in every respect, Hiruta's book deserves a variety of tributes. It is indeed analytically deep and incisive, descriptively precise and elegantly written, leaving readers with a much clearer picture of the nature of the hopelessly entangled relationship between Berlin and his ‘bête noire’. As all the reviewers and several other interlocutors agreed at the aforementioned review session, one of the book's greatest merits is that it provides an unprejudiced and carefully balanced account of both sides (meaning not only Berlin and Arendt, but also their respective acolytes), the quality which is often secretly forfeited despite the alleged declarations of intrinsically reconstructing their thoughts. Thus, the following three reviews are all supportive, while they do provide constructive questions, additions and criticisms. Otobe, for example, argues on the validity of Hiruta's distinction between the ‘Weberian vocational’ approach to political theory and the ‘detached and institutionalized’ one – attributed to the two twentieth-century thinkers at issue and to contemporary analytic political philosophers, respectively – to raise a more fundamental question about the utility of Arendt and Berlin's style of philosophizing today. Yamaoka raises another significant question, which concerns Hiruta's formulation of the difference between Arendt and Berlin in the modelling of the human being. Specifically, he asks Hiruta to expand on whether Berlin could present any substantial vision of humanity in defiance of his value pluralism.

While the three reviews here deal with different aspects of Hannah Arendt and Isaiah Berlin, they have overlapping foci, including Hiruta's own method of combining historicism and politico-philosophical analysis, his characterization of the two thinkers' ‘old’ style of political philosophizing and his account of their complex relationship with Zionism. Otobe discusses the second most extensively, using Jeffrey E. Green's advocacy of a ‘broad, expansive and eclectic political theory’ as a critical point of comparison (see Otobe's review). Meanwhile, Futai dwells on Hiruta's explanation of the difference between Arendt and Berlin over Zionism, adding her own view of this difference based on her published Japanese article (see Futai's review). All the reviews are sincere and critical engagements with the book, and Hiruta offers a thoughtful response with further clarification of his intentions and arguments. I do hope that they help to promote a deeper understanding of and get more out from his book as well as the work of its two protagonists. Finally, I would like to conclude this introduction by expressing my genuine thanks to the editors of the journal for their prompt decision to accept this review forum.