Since Rudra is One, the knowers of Brahmn did not wait in anticipation for a second deity, says the Svetasvatara Upanishad, thereby setting the tone for early Shaivite thought. Unique in its overtly theistic strain, this Mantra Upanishad as it is called by Adi Shankara, is the first to allude to Shiva-Rudra as the Parama-Purusha, and can be considered as a poetic forerunner of the later philosophical tenets of Shaivite traditions, especially the Trika school of Kashmir Shaivism. From Sage Svetasvatara to the philosopher Abhinavgupta there is an unbroken chain of thought which sees Shiva as the Inexpressible Truth which the yogis realise by focusing their minds on the Self.
The Trika tradition of Kashmir Shaivism puts Shiva at the centre of this matrix of Being and Becoming - there is only one Being, Shiva, who is the nature and existence of all beings, filled with the infinite light or prakasha of universal consciousness. The external world, too, is seen as a reflection of this Shiva consciousness, Pratibimbavada, the theory of reflection, where Creation, the Shakti is not external or independent of God-consciousness, but is a mirror of this Shiva principle. It is not separate but one only just as fire is one with its heat, in contrast to the Shankara-Advaita proposition that the outer world is merely a projection of maya or illusion.
Shiva himself forms the basis of this unique monistic thought, since he is shown as being synonymous with the Purusha principle, the underlying Self of the universe, from whom emanates the manifest world, the Prakriti-Shakti principle, and into whom everything dissolves back. The Trika tradition does not stress on the need for a devotional worship of Shiva, but sees the relationship of Shiva and Jiva as one of an inherently existing Oneness and identity. This interplay of the soul and world is defined as Shiva's 'dynamic' first impulse, arousing himself from his static samadhi, in which there is no outer world to manifest.
Through this leela or divine play of Shiva through his Shakti or Creation Shiva himself is able to recognise his own universal consciousness - for otherwise, Abhinavgupta says, there is nothing to recognise, for that consciousness is already there. The Kashmir Shaivite believes that even though every being has this intrinsic knowledge of his Shiva nature, it is overshadowed completely by the mind, the cogito, and its act of incessant thinking by which all beings have got into the habit of defining themselves. To transcend the mind is to find the Shiva nature within oneself, which is to realise that the 'you' and 'i' are actually the same.
This transcendence of mind, Trika says, can be achieved through anavopaya, disciplining the ego or anava through meditative practices, or through the method of saktopaya wherein energy centres are sought to be activated by centring one's attention to the silence which comes up between the end of one thought and the beginning of another, usually not even felt, but ever-present, the Kundalini path.
The path of Grace through total surrender is the third means of recognition - pratyabighna darsana - of one's Shiva consciousness, and Trika believes this to the most effective, the sambavopaya, freedom from thought through the Grace of Sambu-Shiva.
This turning inwards into the origin of thought itself leads one to the fulfilled state of anupaya, where the Jiva sees himself reflected in the image of Shiva himself, and knows that Shiva and Shakti are identical.