Decisively answering a question that has haunted generations of scholars is, and should be, the dream and aspiration of most scientists. Problems such as Fermat's last theorem have become famous in their own right, and producing an answer that would stand the test of scientific criticism is a feat sometimes taking decades of work. When successful, the scientist who has solved such as puzzle is set for life, with grants, students, Nobel prizes, state dinners, lecture tours, book deals, and the usual paraphernalia of success.

Tessa Leesen's book Gaius Meets Cicero is an attempt of similar magnitude. Within Roman law and legal history, the controversies between the schools of jurisprudence have been a perennial issue ever since the publication of Gaius' Institutiones, which was discovered in Verona in 1816. The two schools, Sabinians (known also as Cassians) and Proculians trace their origin to the reign of Augustus and the disagreements between Roman jurists C. Ateius Capito and M. Antistius Labeo, of which the first is reputed to have stepped into the service of the new regime whereas the latter would have maintained the independence of jurisprudence from political power. However, because relatively little is known of the root causes of the controversy, various hypotheses stemming from legal argumentation, political expediency, and philosophical orientation, have been presented. Leesen's main point is that the differences between the schools are to a large extent based on real cases.

Leesen tackles the issue by examining twenty-one known controversies, beginning from the age of male adulthood, and analyzing them based on the arguments of both sides and the context of the issue at hand. She argues that the controversies were practical arguments, with each side supporting their own views, made in the course of legal practice. Because the leaders of the schools had been granted the right to present legally binding expert opinions on matters of law (the ius respondendi or the right to respond), the controversies were settled only by later emperors responding to legal questions. The arguments in the controversies should therefore not be seen as manifestations of divisions between conservatives and progressives, but rather the application of topical argumentation in the way shown by Cicero in the Topica.

The book convincingly argues that most of the modern attempts at explaining the controversies are both contradictory and unconvincing when faced with the evidence, There are a number of issues. The first is that of relying on the ius respondendi as the key point in the argument. The institution, known only from a couple of garbled sources, has a rich history in the mythology of Roman law because it conveniently underlined the importance of jurisprudence. However, from a historical perspective, the consensus has been that in practice no such institution or privilege existed. One would have hoped that the decision to take it as a historical fact would have been accompanied with some discussion on the sources. The second main issue is that of topical argumentation and the influence of Cicero. As the book manages to topple previous modern universal explanations, introducing another one-size-fits-all solution is a surprising choice. Again, one would have hoped to hear more on why similarities in topical argumentation would be conclusive in settling the larger issue of the origins of controversies. The reader struggles at times to separate the known knowns from the known unknowns, for example, the ius respondendi plays the parts of an argument, a fact, and a point to be proven.

In general, the book is well written and contains few errors. The structure of the book is not the most approachable, as the reader has to go through the twenty-one cases and reach almost the end of the book to get to the important part, the analysis. The style reflects the stated intention of the author to solve the issue, which deviates somewhat from the traditional way of emphasizing the nuances of various arguments.

In graduate methodology courses it is often told that in the hard sciences, issues are definitely resolved with experimentations and calculations, but in the humanities and social sciences, asking the questions is more important than providing the answers, because answers tend to be simply fickle interpretations. This book tackles one of the most important issues of the history of Roman jurisprudence, but in the end, it proves the simplistic methodological observation right. The issue remains unresolved, but the debate continues.