 In what follows, most of our discussion will center around the Pramāṇavārttika, as it is by far the largest and most important of Dharmakīrti’s works. It is an unfinished, highly philosophical, commentary on the Pramāṇasamuccaya (“Compendium of Epistemology”) of Dignāga. At various key places in the text we see that Dharmakīrti seems to have formulated some basic ideas as a reaction to now lost commentaries by Dignāga’s students, the most important being the commentary on the Pramāṇasamuccaya by Īśvarasena. A notable reaction to Īśvarasena is Dharmakīrti’s emphasis on certainty (niścaya) (see sections  1.4  and  3.1).  There are also innovations that, as far as we know, were not provoked by earlier commentators. Whether in metaphysics, epistemology or philosophy of language, causal theories carry considerable philosophical weight. These theories are probably to quite a degree original, not found in Dignāga’s own writings. In what follows, we will examine what we consider to be the most salient features of Dharmakīrti’s philosophy, bringing out inter alia the importance of this causal stance. It is however impossible to discuss all the major themes that were traditionally commented upon by Buddhist scholastic writers on Dharmakīrti. Choices and exclusions had to be made. For readers who seek a comprehensive treatment of the historical development of Dharmakīrti’s positions in his seven works, the best reference to date is Eltschinger (2010). Quite detailed summaries of Dharmakīrti’s works are found in Potter (2017).