Brahma Gita is based on the philosophy of Advaita (monism). The teachings are found in the Nirvana Prakarana section of the Yoga Vasistha. It is in the form of a dialogue between Sage Vasishta and King Rama. Brahma Gita text is divided into six chapters, a proper understanding of which leads to liberation from worldly trails.
In Brahma Gita, Sage Vasishta explains to Rama the nature of Absolute Consciousness. Just as an individual is made up of both chetana (consciousness) and achetana (the material body, the Absolute Consciousness, though eternally formless, ‘appears’ also as the insentient universe (I.10-11).
The Infinite Consciousness is called Virat (Universal Self) and the manifest worlds are merely mental constructs like a dream (I.26-27).
The worlds are like waves in the Brahman Ocean and all individuals are only the overflow of the waves. Hence ultimately, there is no duality (II.2). In fact, nothing ever comes forth and nothing is destroyed. The one beginning-less and endless Brahman alone exists (IV.9).
The highest type of existence is the limitless silence, which is called nirvana, turiya and moksha (II.15)
The delusion of duality is overcome through the understanding of the sacred texts and by meditating on their meaning (II.27).
The pith of the teaching of the Brahma Gita is contained in the last verse, which states that, “The seer, the seeing and the seen are only the shining of the Consciousness of the Absolute Reality. Everything that is physically perceived is an empty dream. Hence all universe is also the infinite consciousness. (VII.18).