Rationality in a legal system suggests a consistent set of legal propositions as well as methods for modifying, limiting, and expanding the laws which are governed by some type of logical apparatus. It is a desirable characteristic because it furthers one of the primary ends of a legal system: It facilitates social interaction by enabling members of society to calculate the consequences of their conduct. It is not an easy concept to define, however. Rationality may take different forms, more or less formal, more or less innovative. These different forms shall be examined to determine the type of rationality which characterizes the Islamic legal system compared with the common law. Max Weber and Lawrence Friedman provide the basic framework. Their classification systems for rational and irrational lawmaking and law-finding are fine models for legal analysis and are used extensively in this Article. Their categorization of Islamic law, on the other hand, misses the mark. It is my belief, illustrated by an example of legal reasoning in Islamic contract law, that this widely known but little understood system is a prime example of innovative logically formal rationality (as that term will be defined in this Article) at a point in history when few other legal systems could claim the same.
John Makdisi, Formal Rationality in Islamic Law and the Common Law, 34 Clev. St. L. Rev. 97 (1985-1986)