Before the continuation of our series, reference needs to be made to the most renowned exponent of the Advaita Vedanta school of philosophy, Adi Śaṅkara (700-750 CE), since we shall be utilizing from time to time his commentary on the Māṇḍukya Kārikā. Some have placed his death at 32 years of age but the dates, 700-750, grounded in modern scholarship, are more widely acceptable. He wrote numerous works during his brief stay on this earth, but his monumental work, Brahmasūtrabhāṣya , is considered to be second to none in Indian metaphysics. His teacher was Govinda, who in turn was originally taught by Gauḍapāda. His primary assent to truth is psychological and religious rather than logical; thus, he is perhaps best known as a prominent religious teacher rather than a philosopher in today’s modern terminology.
For the Advaita Vedanta of Shankara, Brahman is the nondual primordial awareness that is Absolute or Ultimate Consciousness Being Itself, “One, without a second,” without limit, empty of all predicates, attributes and qualities, beyond concept and belief, or any subject-object dualism whatsoever.
Nirguna Brahman is pure nondual Being Itself; Saguna Brahman is pure Being in the various states and stages of becoming in spacetime reality. These two Brahmans are not separate entities. These two aspects of the one great Reality, are the ontologically prior union of the dualism of being and becoming, of emptiness and form, of the Two Truths that are one absolute reality with its arising, unfolding relative phenomenal appearances. “The One is. The One is not” (Plato, Parmenides).
For Shankara then, Nirguna Brahman is the non-experiential, non-conceptual, uncreated nondual Base in whom arises the always present enlightened, pure luminous witness presence, the bright vidya of the Atman-Self that is only Brahman abiding at the heart of all beings. (David Paul Boaz, Shankara’s Advaita Vedanta)
Truth be told, however, he was no avid fan of Buddhism. There were times when he used his knowledge of Buddhism to attack Buddhist doctrines harshly or to convert them into his own Vedantic nondualism; and he even tried with great gusto to “vedanticize” the Vedanta philosophy, which had been made extremely Buddhistic by his predecessors. The basic structure of his philosophy is more akin to Samkhya, a philosophic system of nontheistic dualism, and the Yoga school than to Buddhism. At the same time, one could say that his approach did not greatly exaggerate any indifference to Buddhist methodology in itself. Yet for all this, Buddhism did him no favors in return. Śaṅkara is not mentioned even a single time in any Buddhist or, for that matter, any Jain philosophical work.
However, to the nondual mind of enlightenment—the view of Ultimate Truth—the egoic jivatma self is always changing and impermanent, while the Atman-Self is unseparate from, identical to, and arises within the monadic, changeless, timeless, spaceless Nirguna Brahman, the nondual Ultimate Supreme Source. And, this is analogous to Mahayana shunyata/emptiness. Again, the Atman-Self that is Brahman is empty of all predicates, including inherent existence. The Truth—emptiness, Dharmakaya, etc. —is said to be empty in essence, luminous clarity in its nature, and compassionate in its energy expression. This could be said of Nirguna Brahman as well. Therefore, the Buddhist criticism targets only the outer exoteric, theistic, dualistic Hindu view of Brahman, and not the more subtle nondual view of Advaita Vedanta. (ibid)