The present work contains an English translation of the Ornament of Reason (Tib. dBu ma'i rtsa ba shes rab kyi 'grel ba thad pa'i rgyan), an influential 12th century Tibetan commentary to a classic of Indian Buddhism, Nàgàrjuna's Root of the Middle Way (Skt. Mûlamadhyamaka-kârikâ Tib. dBu ma'i rtsa ba shes rab ces bya ba). The author, rMa bya byang chub brtson 'grus's, was among the first Tibetans to explicitly align themselves with the philosophical project of the 7th century Indian Madhyamaka teacher, CandrakTrti. With his stern revision and transformative re-employment of the epistemological framework that CandrakTrti otherwise scorns, rMa bya was however to develop an original and highly influential Madhyamaka interpretation.¦rMa bya's "topical outline" (Tib. sa bead) of his commentary is contained in the first appendix to the translation. The second appendix contains a digitalized version of the Rumtek edition of rMa bya's commentary, cross-referenced to the page numbers of the translation. The annotations contain concise explanatory remarks and suggestions for further reading, as well as identifications of the passages that rMa bya cites.