A collaboration of leading historians of European law and philosophers of law and politics identifying and explaining the practice of interpretation of law in the 18th century. The goal: establishing the actual practice in the Age of Enlightenment, and explaining why this was the case. The ideology of the Age was that law, i.e., the will of the sovereign, can be explicitly and appropriately stated, thus making interpretation redundant. However, the reality was that in the 18th century, there was no one leading source of national law that would be the object of interpretation. Instead, there was a plurality of sources of law: the Roman Law, local customary law, and the royal ordinance. However, in deciding a case in a court of law, the law must speak with one voice. Hence, interpretation to unify the norms was inevitable. What was the process? What role did justification in terms of reason, the hallmark of the Enlightenment, play? These are some of the questions addressed.