Pratyabhijna, recognition, is the term the Kashmiri non-dual school uses for its central claim, and Abhinavagupta inherited rather than invented it, from his teacher's teacher Utpaladeva, whose Ishvarapratyabhijnakarika argued that liberation is not the acquisition of a new state but the recognition of the self's own always-present identity with Shiva, obscured by nothing more than a failure to notice it. Abhinavagupta's major philosophical contribution was to write the great commentary on Utpaladeva's work, the Ishvarapratyabhijnavimarshini, that made the argument rigorous enough to answer the Buddhist logicians of the day on their own technical ground, and then to fold that entire philosophical apparatus into the wider synthesis of the Tantraloka.
The claim has a specific shape worth stating carefully. It is not that the world is illusory in the sense of being unreal, and not that the practitioner must withdraw from ordinary experience to find the divine elsewhere. Shiva, on this account, is not other than the world; the world is Shiva's own free self-manifestation, vimarsha, the dynamic self-awareness by which pure consciousness knows itself as agent rather than remaining an inert light with nothing to illuminate. What obstructs recognition is not distance from the divine but a contracted, limited sense of selfhood, and what the Tantraloka's graded practices are for is loosening that contraction until the practitioner recognises, rather than attains, an identity that was never actually absent.
This is why Abhinavagupta treats even the most ordinary or embodied experience, including aesthetic and, in the Kaula current, ritualised sexual practice, as potentially revelatory rather than as an obstacle to be transcended: anything, approached rightly, can be the occasion on which the always-present recognition occurs.