Scholarship on Islamic law has been generally wary of approaching Islamic law from literary perspectives. Muslim tradition understands Islamic law to be composed of legal theory (usul al-fiqh) and positive law (mutun/fiqh) and modern scholarship has tended to reflect this division. In looking at the field of Islamic legal literature through a literary perspective, however, one discovers a tremendous variety of legal genres—different modalities through which to understand the law. The variety and spread of varying legal genres, a phenomenon which blossomed in the 12th and 13th centuries, raises the question of why a multiplicity of genres became attractive to legal scholars. My paper is an analysis of the function of one such genre, that of legal distinctions (al-furuq al-fiqhiyya), and looks at how this genre was used to understand and develop laws on purity (tahara) within the Hanafi legal school. I take three books as a case study for my analysis, Kitab al-Furuq by Muhammad ibn Salih al-Karabisi (d. 322), Kitab al-Furuq by As‘ad ibn Muhammad al-Karabisi (d. 570), and al-Ashbah wa-l-naza’ir by Ibrahim Ibn Nujaym al-Misri (d. 970). Muhammad al-Karabisi was the first Hanafi to author a book on legal distinctions; As‘ad al-Karabisi wrote one of the most widely circulated book on legal distinctions approximately 200 years after Muhammad al-Karabisi; and finally, Ibn Nujaym’s al-Ashbah wa-l-naza’ir was a cornerstone of legal thought throughout the Ottoman Empire and the integration of this genre into legal encyclopedic works. As such, each work represents a particular moment in the history of this genre and was an important contribution thereto. My paper will analyze the way that “distinctions-thinking” was utilized in each of these three works. A typical entry in a book of distinctions compares two apparently similar law and then discusses the distinction between these laws, the distinction that makes them different laws. I analyze the set of laws being distinguished by singling out the two laws, the similarity between them, and the distinction. In so doing, my paper will show the vibrancy and dynamism inherent in furuq writing. I show that rather than simply repeating the information contained in contemporary legal compendia (mukhtasar), the distinctions belied a sophisticated and distinct method of legal thinking. This thinking reveals added complexity and nuance that underlay Islamic legal thinking into the Ottoman period and help reveal a level of legal dynamism hindered by up-to-now traditional approaches of the law.