Abhinavagupta (950–1020 CE) was a master syncretist, who discovered the thread of unity underlying the divergent spiritual thought-currents that had their origin and development in successive periods of time. In his magnum opus, Tantraloka and Paratrimshika, he has said that the spiritual thought-currents known as Agama, Spanda, and Pratyabhijna are not divergent in nature, but these are mutually complementary.
Historically speaking, these represent three successive phases in the development of the Advaita Shaiva philosophy in Kashmir. He has therefore named it as the Trika school of Shaivism.
Abhinavagupta has mentioned three triads, trika, in his magnum opus Tantraloka as constituting the subject matter of the Trika school of Shaivism. These are: Shiva, Shakti, and their union; Shiva, Shakti, and Nara; and Para Shakti, Apara Shakti, and Parapara Shakti. He has projected the idea of their essential identity bynaming the Advaita Shaiva school of spiritual philosophy as Trika.
Abhinavagupta borrowed spiritual thoughts from the Chumma tradition that was then popular with the common masses in Kashmir, and assimilated them in the spiritual philosophy named by him as Trika.
It may be mentioned here that no literature was available to Abhinavagupta then, which is evident from his quoting verses in the local dialect without naming the source and incorporating them at the end of some chapters of his work, Tantrasara. In this manner, Abhinavagupta made the Advaita Shaiva philosophy, the most perfect and powerful school of spiritual philosophy in Kashmir, eclipsing the popularity of other schools like Saiva Siddhanta, Yogacara Buddhism, and Pancharatra Vaishnavism in Kashmir.
Source - article titled 'Light on Abhinavagupta’s Contribution to the Advaita Shaiva Spiritual Philosophy of Kashmir' by Dr Debabrata Sen Sharma published in Prabuddha Bharata Magazine January 2016 Issue.