Book excerpt: In fourteenth- and fifteenth-century Tibet there was great ferment about what makes enlightenment possible, since systems of self-liberation must show what factors pre-exist in the mind that allow for transformation into a state of freedom from suffering. This controversy about the nature of mind, which persists to the present day, raises many questions. This book first presents the final exposition of special insight by Tsong-kha-pa, the founder of the Ge-luk-pa order of Tibetan Buddhism, in his medium-length Exposition of the Stages of the Path as well as the sections on the object of negation and on the two truths in his Illumination of the Thought: Extensive Explanation of Chandrakirti's Supplement to Nagarjuna's "Treatise on the Middle." It then details the views of his predecessor Dol-po-pa Shay-rap Gyel-tsen, the seminal author of philosophical treatises of the Jo-nang-pa order, as found in his Mountain Doctrine, followed by an analysis of Tsong-kha-pa's reactions. By contrasting the two systems—Dol-po-pa's doctrine of other-emptiness and Tsong-kha-pa's doctrine of self-emptiness—both views emerge more clearly, contributing to a fuller picture of reality as viewed in Tibetan Buddhism. Tsong-kha-pa's Final Exposition of Wisdom brilliantly explicates ignorance and wisdom, explains the relationship between dependent-arising and emptiness, shows how to meditate on emptiness, and explains what it means to view phenomena as like illusions.