This chapter examines the role of legal science in relation to Max Weber's and Hans Kelsen's theories. It is possible to use Weber's and Kelsen's schemas in legal history to confront and combine their approaches towards past legal systems. Weber and Kelsen share the common fate of a rather bad reception among legal historians of the twentieth century. Max Weber's analysis of the process of law is more sophisticated and historically anchored than the brief remarks from Kelsen about the emergence and developments of legal orders. Kelsen's abstract conception of the influence of the constructed legal order upon the normative order is rendered more determinate through Weber's conception of the subjective representation of law and the ‘empirical legal order’. Weber was very attentive to the resemblances and differences between Roman and Islamic legal science. The chapter ends with the praise of the systematic work of Roman jurists and of the subsequent development of legal concepts from Roman origins.