One of the ideas emphasized by modern Muslim reformers is the need to return to the original sources of Islam in order to acquire an authentic understanding of the religion’s teachings. Some studies (e.g., Bauer 2021; Hamdeh 2021) argue that this modern discourse constitutes a break from the pre-modern Islamic jurisprudential tradition. According to this argument, the reformers’ idea of “going back to the origin” enables them to break free from the restrictions of the traditional interpretations. Other studies (e.g., Brown 2015; Lauzière 2015) show a certain degree of continuity of this modern discourse with discursive approaches found in the pre-modern Islamic tradition. To contribute to this discussion, my paper tries to answer the question of whether the modern discourse of “going back to the origin” is fully or partially continuous with a pre-modern Islamic discourse. By comparing the application of this discourse in Muḥammad ʿAbduh and Rashīd Riḍā with the discourse of Ibn Ḥazm, a supposed ancestor of this idea, I argue that the modern discourse of “returning to the origin” is structurally different from the apparent similar discourses found in the pre-modern Islamic tradition. I formulate my argument through the analytical concept of multiple rationalities. I argue that the practice of fiqh found in the pre-modern Islamic tradition was based on multiple vertical rationalities. In the pre-modern tradition, the first layer of rationality was called pure reason (al-ʿaql al-mujarrad), which consists of a rationality shared between all people. The practice of pure reason is manifested in the tradition of theology (ʿilm al-kalām). However, when it comes to the practice of fiqh, pre-modern jurists depended on another layer of rationality they called dependent reason (al-ʿaql ghayr al-mustaqill) or restricted reason (al-ʿaql al-muqayyad), which consists of rationality that is derived from the Shariah’s sources and the inherited practices from the previous generations. This rationality is manifested in the genre of legal theory (uṣūl al-fiqh). Through a discussion of Ibn Ḥazm, I will argue that pre-modern jurists who emphasized the return to the origin and neglecting schools of law (madhāhib) did not dismiss the dependent reason. Rather, they aimed to establish a distinct dependent reason from the ones established by other schools. However, modern reformers, such as ʿAbduh and Riḍā, were influenced by a Cartesian conception of rationality. This is discerned in their dismissal of the second layer of rationality and their dependence on pure reason when reading the sacred texts.