  Gaṅgeśa’s Tattvacintāmaṇi is divided into four parts, one for each of the four knowledge-sources or pramāṇas recognised by the Nyāya school. The post-Gaṅgeśa scholars focused more and more exclusively on the second part, concerning inference, and wrote increasingly detailed commentaries on a comparatively small portion of the book, namely the part where Gaṅgeśa examines the relation between inferential sign and property-to-be-inferred, which is called the vyāpti, ‘pervasion’ or ‘inference-warranting’ relation (Ingalls 1951, Goekoop 1977, Wada 2007). Even today, in a traditional Indian education, study of these sub-commentaries on various subsections of the vyāpti section of Gaṅgeśa forms an essential part of the curriculum.