This chapter will introduce the basic, theoretical architecture of competing Islamic natural law theories from the pre-modern period (ninth to fourteenth centuries). Specifically, it will outline juristic debates in the usul al-fiqh genre on reason as a source of law, where revelation is silent. Thereafter it will reflect on a range of doctrinal debates in which many of those same pre-modern jurists came to a legal determination without reference to scriptural (or any other) texts. Drawing on a curious heuristic they labelled huquq Allah and huquq al-ʿibad (the claims of God and the claims of individuals), I will show that despite not invoking (expressly or otherwise) any natural law account of Islamic law, jurists nonetheless developed law based on a mode of rationality that could be called anything from ‘rational’ to ‘common-sense’ to ‘pragmatic’.