Phillip Ackerman-Lieberman's study of commercial partnership re-examines business relations among medieval Jews using evidence from the Cairo Geniza (a cache of documents, ranging from shopping lists to liturgical texts, most of which date from the tenth to the thirteenth centuries, which were preserved in a synagogue in Cairo). Based on his findings, Ackerman-Lieberman calls into question the prevailing models used to understand the relationship between legal theory and legal practice, as well as the ways in which Jews interacted with the broader Muslim-majority society in which they lived. Although his historiographical interventions are aimed primarily at scholars of the Geniza, his conclusions speak to more general methodological questions about how to approach the study of law as it was actually experienced and practiced. His suggestions are especially relevant to the medieval context in which documentary evidence is often fragmentary or absent altogether.

Ackerman-Lieberman's principle innovation is to look closely at legal documents as evidence for the legal principles by which merchants organized their partnerships. Although this approach may seem self-evident, especially to scholars of law and history, the scholarship on commercial organization in the Geniza has heretofore relied mainly on commercial letters. S. D. Goitein, father of the “Princeton School” of Geniza studies, and Abraham Udovitch, who wrote the first in-depth study of partnership in the Geniza, both relied on letters exchanged by merchants to make arguments about the nature of commercial cooperation. Goitein and Udovitch concluded that Jews relied mainly on models of partnership that followed Islamic law, of which the commenda (Arabic qirad) was the most popular. Ackerman-Lieberman draws on partnership agreements, release documents, and other such formal legal instruments (of which he provides fifteen full transcriptions and translations in an appendix) in order to argue that intra-Jewish commercial cooperation adhered quite closely to the prescriptions of Jewish law concerning partnership. Ackerman-Lieberman explains in detail the ways in which Jewish and Islamic partnership law differ, mainly concerning the amount of risk and responsibility assigned to the agent. He then proceeds to offer compelling evidence that the majority of legal documents documenting partnership in the Geniza actually complied with the Jewish law of partnership.

Having concluded that most Jewish merchants did not choose Islamic legal models, Ackerman-Lieberman embarks on a broad critique of methodological approaches to studying the Geniza. (He opens the book with this historiographical intervention, which usefully frames the often technical arguments about partnership law in a broader conversation about sociolegal history.) He interrogates scholars' understanding—especially those of the Princeton School—concerning the connection between the commercial and legal practices of Jews and those of Muslims. In other words, he asks to what extent can we extrapolate from Jews' business practices (which are well documented in the Geniza) to the broader commercial culture. Ackerman-Lieberman shows that Goitein, Udovitch, and others build in assumptions about the kinship between Jewish legal and commercial practice—and Jewish society more broadly—and the legal and commercial practices of the Muslim majority. This approach allowed Udovitch to use Jewish commercial letters in order to draw conclusions about the “law merchant” of the Muslim-majority society, and consequently to argue that the legal practice of the medieval Islamic world closely resembled Islamic legal theory. However, if we cannot merely assume that the commercial practices of Jews reflected those of their Muslim neighbors—because, Ackerman-Lieberman argues, Jews mainly relied on Jewish legal models—then a number of important questions arise. What was the relationship between Jewish legal practices and those of non-Jews? Whence can we glean information about Muslim legal practices?

In the final chapter, Ackerman-Lieberman offers a new model for understanding both the relationship between commercial cooperation among Jews and Jewish law and the relationship between Jewish practices and those of the broader Islamic society in which these Jews lived. His “specular-relational model” focuses on “the deep structure of society rather than the simple comparison of details” (204). By rejecting the idea that one culture (usually the minority) simply borrows legal, commercial, and social norms from another (usually the majority), Ackerman-Lieberman instead proposes to focus on the “creative confrontation” among cultures. Rather than merely assuming that Jewish society borrowed its mentalité from Muslims, he asserts that different aspects of Jewish life had different relationships (rejection, adoption, synthesis) to the dominant Islamic culture. Thus Jewish commercial partnerships drew mainly on Jewish law—and, he suspects, Muslim partnerships drew mainly on Islamic law—but this does not mean that all aspects of Jewish life were determined exclusively within a Jewish framework.

Ackerman-Lieberman's book offers an important historiographical intervention in Geniza studies and medieval economic history. For legal historians, his approach is most useful as an interrogation into the models that often implicitly shape our understanding of the relationship among different legal orders and legal practices that coexisted in legally pluralist environments.