Advaita Prakarana is the third chapter of Gaudapada’s Mandukya Karika, a commentary on Mandukyopanishad. Mandukya Karika (6th century CE) is also known as Gaudapadiyakarika or Agama Shastra. This is widely accepted as the earliest text on Advaita.
Advaita Prakarana, consisting of forty-eight karakas (stanzas), discusses the nature of Advaita (non-duality). It says the Supreme Reality is non-dual, beyond all limitations, unborn and homogeneous. The individuality of selves derives from their apparent delimited nature. Just like akasha (space), the Self is also beyond birth and death and it is omnipresent. The individual self is neither a real transformation nor a part of self. All the aggregates of the phenomenal world are mere epistemic projections affected by maya. The entire phenomenal realm is characterized by epistemic projections of Advaita. Thus, the realm of duality is the realm of epistemic appearances.
The inscrutable magical nature of maya makes possible the epistemic projection of the immutable non-dual Self is the absolute ontological Reality, whereas the realm of duality is merely its epistemic product.
Gaudapada says the Self described in Taittiriya Upanishad, as living within pancha koshas (five sheaths), and in Madhukansa of Brihadaranyaka Upanishad, is identical with the Supreme Self or Brahman. The talk of distinction of jiva (individual self) and Supreme Self is meant only for convenience of instruction and it is of secondary importance.
The world of duality appears so, as the mind takes on dual aspects (of subject and object) due to maya. Therefore, perfect control of the vigilant mind, in the form of stilling of tall dualistic concepts in the state of Samadhi, leads to the realization of the omniscient, omnipresent, immutable, fearless, tranquil and effulgent supreme Brahman. In this state, the mind is one with Brahman and this is known as asparshayoga (conjunction without contact).