Tsong khapa (14th-century) is arguably the most important and influential philosopher in Tibetan history. An Ocean of Reasoning is the most extensive and perhaps the deepest extant commentary on Nagarjuna's Mulamadhyamakakarika (Fundamental Wisdom of the Middle Way), and it can be argued that it is impossible to discuss Nagarjuna's work in an informed way without consulting it. It discusses alternative readings of the text and prior commentaries and provides a detailed exegesis, constituting a systematic presentation of Madhyamaka Buddhist philosophy. Despite its central importance, however, of Tsong khapa's three most important texts, only An Ocean of Reasoning remains untranslated, perhaps because it is both philosophically and linguistically challenging, demanding a rare combination of abilities on the part of a translator. Jay Garfield and Ngawang Samten bring the requisite skills to this difficult task, combining between them expertise in Western and Indian philosophy, and fluency in Tibetan, Sanskrit, and English. The resulting translation of this important text will not only be a landmark contribution to the scholarship of Indian and Tibetan Buddhism, but will serve as a valuable companion volume to Jay Garfield's highly successful translation of The Fundamental Wisdom of the Middle Way.