Trika philosophy is intended for any human being without restriction of caste, creed, or color. Its purpose is to enable the aspirant to rise from Individuality to Universality. Trika Shastra, Bhairava Tantras or Kashmir Shaivism are the same.
During the beginning of current period i.e. Kalayuga , the ancient philosophy of SHAIVISM which as per some accounts originated during Chalcolithic Age 5000 BCE was slowly loosing relevance and fading away. At that time Lord Shiva camein the form of Lord Shrikant Nath and invited Sage Durvasa to his abode i.e.Mount Kailash and ordered him to once again revive this philosophy.
He fully initiated sage Durvasa, into all forms of the Tantrika knowledge, including abheda (without differentiation), bhedābheda (with and without differentiation), and bheda (differentiated), as described in the Bhairava Tantras, Rudra Tantras, and Śiva Tantras, respectively. Durvasa Ṛeṣiintensely meditated in the hope of finding an adequate pupil to initiate, butfailed to do so. Instead, he created three “mind-born” sons, and initiated the first son, Tryambaka fully into the monastic abheda philosophy of the Bhairava Tantras; This process continued till fifteen generation. Then descendant Sangmaditya was unable to create a son with the power of mind. He wandered throughout the land and finally reached Kashmir (Indian State of Jammu & Kashmir). In Kashmir he married a girl and settled there and began to propagate Trika philosophy in Kashmir thus to be known as KASHMIR SHAIVISM.
Recent historical view
There was a famous ruler in Kashmir from 724-760 C.E. named King Lalitaditya. Lalitaditya managed to create an empire that included majorparts of India as well as present-day Afghanistan and Central Asia. During his conquestof Antervedi a village near the intersection of river Yumana and Ganga, he met sage Atrigupta. King was deeply impressed by sage Atrigupta’s Shiva teachings and invited him to live in Kashmir and teach Shaivism. From there the teachings of Bahirava Tantra spread throughout the world and were centered in Kashmir. From Atrigupta the line of teachers of Kashmir Shaivism descended. The great philosopher Abhinavagupta was from the same lineage i.e. son of Narshisamagupta who was son of Varagupta.