 One of the earliest attempts in this context is Thābit Ibn Qurra’s theory of the psychology of mathematical invention. However, it was probably his grandson, Ibrāhīm Ibn Sinān (d. 946), who established an independent area of studies pertinent to the aforementioned questions in his On the Method of Analysis and Synthesis in the Problems of Geometry (R. Rashed &amp; Bellosta 2000: chap. I). He categorizes geometrical problems into different groups based on different criteria and, providing concrete examples, explains how each group of problems must be analyzed (taḥlīl) and how a solution for them can be synthesized (tarkīb). He highlights the possible errors and mistakes that one might make in the process of analysis and synthesis and elaborates how they can be avoided. The next important figure in this area is al-Sijzī (d. ~1020), who wrote a book (Geometrical Treatise on Problem Solving) on different methods which can facilitate the procedure of problem solving in geometry. But the most mature work among these kinds of studies is perhaps Ibn al-Haytham’s Fī al-taḥlīl wa al-tarkīb (On Analysis and Synthesis; R. Rashed 2006 [2017: 219–304]). An interesting issue discussed in this area of philosophy of mathematics was the nature of undecidable problems; claims for whose truth or falsity we have no proof. This issue was discussed in particular by al-Samawʾal (d. 1180) in the context of the classification of geometrical problems in his al-Bāhir fī al-jabr. His classification project can be understood as a succession to that of Ibn Sinān (R. Rashed 1984b [1994: 41–43]; 2008: sec. 3; 2015: 726–32).