The Isvarapratyabhijnakarika (IPK) of Utpaladeva (early X century C.E.) is the foundation stone of the Pratyabhijna school and constitutes the main theoretical framework of the Trika. It is the most important philosophical work of non-dual tantric Shaivism as a whole. Utpaladeva devoted two commentaries to his IPK, a vrtti and, later on, a tika. or Vivarti (now almost totally lost). According to Abhinavagupta, the IPK and the vrtti thereon were composed by Utpaladeva at the same time. This makes the vrtti and indispenable tool to grasp the original meaning of the difficult karikas of the Isvarapratyabhijna. Unfortunately, all vrtti manuscripts from Kashmir break off at the same point, and consequently, so did the edition (also faulty in many points) published in the Kashmir Series of texts and studies in 1918. The present book, originally published in the Serie Orientale Roma (IsMEO), contains the first critical edition of the IPK and, for the first time, the complete text of the Vrtti on the basis of a unique Malayam manuscript discovered in Trivandrum Library by R. Torella, who has also made use of the other incomplete manuscripts from Kashmir. The edition is accompanied by an English translation with copious exegetical notes, which highlight the connections of Utpaladeva's thought with the coeval schools of Indian philosophy and, first of all, with the Buddhist pramana tradition. The book is completed by an elaborate Introduction, three Indexes and a Bibliography.