In Comparative Matters: The Renaissance of Comparative Constitutional Law, Ran Hirschl considers the contemporary state of comparative constitutional law and surveys some of the highlights in its rich and varied intellectual heritage. Hirschl ponders the future of the field and argues that comparative constitutional research could be enriched if scholars adopted a more interdisciplinary approach. According to Hirschl, artificial divides among closely related disciplines examining the same constitutional law phenomenon, “limit the scope, depth, and breadth of the questions we can address, the choice of methods we make, and the kinds of accounts we can offer” (p. 190). In particular, Hirschl seeks a closer connection between constitutional comparativists and the social sciences which offer “[m]any of the tools necessary to engage in the systematic study of constitutionalism across polities” (p. 190). By encouraging interdisciplinarity, Hirschl envisions scholars moving beyond “thin” doctrinal comparisons of constitutional law to engage more with context, which can provide a fuller understanding of constitutional developments – an approach Hirschl terms “comparative constitutional studies”.

In the first chapter, Hirschl asks the revealing questions of how and why courts engage in comparative constitutional law research. In interpreting broadly worded rights guarantees that are open to different interpretations, judges cannot avoid engaging with politics (whether this is acknowledged or not). As part of the decision-making process in such cases, judges might look at jurisprudential developments elsewhere, typically in a select club of countries that are perceived to share similar values – something Hirschl describes as “cherry-picking”. This foreign jurisprudence is used by courts for a number of purposes including principled consideration, self-reflection, and opportunism in the sense that foreign law can provide a grounding for the legal reasoning to be applied in the case. Hirschl then evaluates these views through a detailed case study on the use of comparative law at the Supreme Court of Israel. The book's second chapter finds Hirschl drawing parallels between the questions debated by modern constitutional comparativists and the history of interactions between Jewish law and its legal environment, which includes many of the world's past and present legal traditions. The aim here is to better understand the driving forces behind selective comparison while the broader point is that constitutional comparativists have an untapped opportunity to shed light on current issues by examining how past traditions viewed and dealt with similar problems. According to Hirschl, “the near-exclusive focus on the present in comparative constitutional studies obscures the fact that some of the core conundrums the field is facing are not new” (p. 80).

In the third chapter, Hirschl traces the development of the field by highlighting “epistemological leaps” in comparative constitutional law from the sixteenth century to the present by way of short profiles that highlight contributions of key figures including John Bodin (questioning the relevance of Roman law in France through wide-ranging comparative studies), John Selden (studying Jewish law as a potential source of universal legal norms), Montesquieu (analysing and classifying laws and governments), and Simón Bolívar (using insight gleaned from comparing constitutional developments to advance a political agenda). From this historical foundation, Hirschl advances his own leap forward by making the case for a transition of the field of comparative constitutional law, which has been dominated by law schools, to the broader discipline of “comparative constitutional studies” (chapter 4). Here Hirschl advocates a closer connection between legal scholarship and the social sciences, which offer well-developed theories of judicial behaviour that promise to improve our understanding of constitutional developments beyond the “thin, ahistorical, and overly doctrinal or formalistic accounts” offered by exclusive or predominant legal analysis. In Hirschl's view, “[c]ulture, economics, institutional structures, power, and strategy are as significant to understanding the constitutional universe as jurisprudential and prescriptive analyses” (p. 152). Put another way, the broader perspective provided by the social sciences can better situate constitutional laws and institutions within their contextual environment and provide a more fulsome understanding of the various attributes of those laws and institutions.

In light of his call for scholars to move toward “comparative constitutional studies”, Hirschl takes stock of the epistemological and methodological challenges that face modern constitutional comparativists (chapter 5). One especially illuminating part of the chapter is Hirschl's discussion of the tension between “universalists” (who focus on common elements among different legal systems and traditions) and “particularists” (who emphasise the unique and idiosyncratic nature of individual legal systems). Hirschl focuses on the universalist versus particularist debate in the area of legal transplants, looking to the work of universalists such as Alan Watson and contrasting it with culturalists like Pierre Legrand. The debate continues in the tension between supranational norms and local traditions and Hirschl provides a number of intriguing illustrations. The chapter moves on to discuss the so-called “northern selection bias” in the design of many English-language studies, which tend to focus on constitutional developments in the liberal democracies of European and North American states. Hirschl rightly points out that very few studies examine or even refer to the laws or institutions of highly populated and globally significant countries such as Indonesia, Pakistan, Nigeria, Bangladesh, Mexico, the Philippines, and Vietnam (pp. 211–12). Instead, constitutional comparativists tend to make generalisations from small and unrepresentative samples and present these observations as universal truth. While accepting the basic premise of the northern selection bias, Hirschl deconstructs the problem and highlights methodological difficulties that will be encountered by scholars seeking to study constitutional developments outside the club of northern liberal democracies.

In chapter 6, Hirschl maps out and critiques the approaches to comparative constitutional law case selection and research design. Hirschl provides a valuable account of the prevailing methodological approaches including studies that focus on the most similar cases, the most different cases, the prototypical cases, the most difficult case, and the outlier cases. He also classifies the objectives of comparative constitutional law studies into a deep, contextualised understanding of a single case, self-reflection, or betterment through analogy, distinction, and contrast, generating concepts and analytical frameworks for thinking critically about constitutional norms and practices, and theory-testing and explanation through causal inference. The chapter reveals the wide range of approaches used by constitutional comparativists. In the end, Hirschl encourages scholars to diversify their approaches in order to “reach stronger, more meaningful conclusions about constitutional law and institutions worldwide” (p. 277). In particular, Hirschl advocates the use of large-N studies, being large-scale empirical surveys, which can offer a refreshing dimension to studies in comparative constitutional law by “[t]racing broad patterns and formulating general rules applicable across contexts” (p. 276). While large-N studies might overlook nuance and contextual detail in individual cases, they can provide a useful addition to the methodological choices of scholars and can be combined with smaller case studies to utilise the advantages of both approaches.

Given a renewed interest in comparing constitutional law and legal institutions across states in the pursuit of good governance, Comparative Matters will be relevant to a broad audience of scholars, especially those with an interest in the history, theory, and method of legal comparison. It will also be of use to judges, especially those of appellate courts, who occasionally engage in comparative constitutional research (as discussed by Hirschl in chapter 1). The book is easy to read, being replete with interesting anecdotes and short case studies. Hirschl's call for legal scholars to adopt a more contextualist perspective in their research, which has been advocated by others such as Armin von Bogdandy, should be applauded. There is much merit in the view that context matters and legal scholars have a great deal to learn from other disciplines. Law and its institutions do not exist, operate, or evolve in a vacuum. There is some degree of risk, however, in encouraging interdisciplinarity, particularly if comparative constitutionalists begin to dabble in fields outside their expertise. As Koen Lemmens has observed, comparative lawyers have been known to incorporate “bits and pieces” from other established disciplines, such as economics, history, and political science, without having received the necessary training or having a good understanding of those fields (particularly their limitations). Legal comparativists might therefore engage with other disciplines on a superficial – or, even worse, misguided – basis. This risk might be managed by a detailed review of the methodological choices made and the results obtained from experts within the relevant disciplines. A second challenge to Hirschl's argument is that, by emphasising context and invoking the methodological tools and perspectives of other disciplines to help explain legal phenomena, the quality and rigour of legal analysis in the scholarship might decline in favour of these non-legal fields. Despite these risks, there is much room in the field for a diversity of approaches to flourish and Hirschl's view of “comparative constitutional studies” set out in Comparative Matters makes a valuable contribution to that end. Its influence is likely to be felt for years to come.