Abhinavagupta (ca. 975-1025 CE) is the greatest synthesizer of Indian Tantric thought and practice. His works influenced and shaped theoretical paradigms in the field of Indian aesthetics, Tantra, literature, and philosophy. In this paper, the author examines the 105 verses of Abhinavagupta’s Paramārthasāra (Quintessence of the Highest Purpose) in which Abhinavagupta articulates his philosophy of absolute monism, known popularly as Kashmir Śaivism. An earlier Paramārthasāra was composed by the South Indian legendary saint, Ādiśeṣa during the sixth century, some four hundred years before Abhinavagupta. Abhinavagupta’s reinvention of this older text indicates the constant transaction of ideas between Kashmir and South India, Vaiṣṇavite and Śaivite sects. The present shape of Indian thought emerged only as a result of the fusion and appropriation of different thought-streams. A translation of the Paramārthasāra along with an introduction into Abhinavagupta’s Monistic Śaivism has been herewith attempted.