Advaitavādīs claim that Ultimate Reality is nondual pure consciousness alone, without form or attributes. They try to define Ultimate Reality only in negative terms, and so they repeat the aphorism neti neti, “not this, not this.”

To support their arguments, they cite Vedic declarations:

• “Indeed, all this is Brahman” (sarvaṁ khalv idaṁ brahma, CHU 3.14.1)
• “Brahman is one alone, without a second” (ekam evādvitīyam, CHU 6.2.1)
• “Brahman is consciousness and bliss” (vijñānam ānandaṁ brahma, BAU 3.9.28)
• “Ultimately no variety whatsoever exists in this world” (neha nānāsti kiñcana, BAU 4.4.19)

According to the Advaitavāda doctrine, the difference between Īśvara and the jīva is not intrinsic or eternal; it is due only to upādhis, or the apparent limitations of Brahman by māyā’s vidyā and avidyā potencies.

When a jīva develops spiritual knowledge and thus transcends these upādhis, he realizes himself to be the unlimited, nonvariegated Brahman. This attainment is supposed to be the perfection of spiritual life.

In support of this concept, the Śaṅkarites quote the Vedic statement, “There is no liberation without direct intuitive insight” (ṛte jñānān na muktiḥ).

The Advaitavāda philosophers hold that there is only one reality — the formless, attributeless, indivisible, non-variegated, impersonal Brahman — and they have various theories for explaining the apparent separate existence of the jīva and Īśvara.

The following two theories are most prevalent, and both have been expressed in several modified forms.

• pariccheda-vāda (the delimitation of Brahman)
• pratibimba-vāda (the reflection of Brahman)

- Tattva Sandarbha (Anuccheda 36)

Learn more: The Vaiṣṇava Concept of Māyā

Learn more: Advaita Vedanta, Shastra

In Śaṅkarācārya’s radical nondualism, existence (sattā) is understood to be of three different grades — prātibhāsika (illusory existence), vyāvahārika (empirical existence), and pāramārthika (ontological existence).

Prātibhāsika existence is perceived in such states as dreams and illusions but ceases when normal consciousness returns.

Empirical reality (vyāvahārika-sattā) refers to our perception of the material world in ordinary waking consciousness, which is executable, meaning that the objects perceived are the support for practical action.

Ontological reality, pāramārthika-sattā, is immanent in all objects of the material world, pervading them as the conscious, blissful source of all manifest varieties.

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Monists say that māyā is neither sat (real), asat (false), nor a combination of both. It is different from both, and yet not non-existent. Thus, it is inexplicable, or anirvacanīyā, and antagonistic to knowledge.

Śaṅkarācārya describes māyā as follows:

Māyā is neither sat nor asat, nor is it a combination of sat and asat. It is neither different from, nor one with, Brahman, nor is it different from and one with It simultaneously. It does not have limbs or divisions, nor is it without them, nor is it a combination of both of these conditions. Māyā is most astonishing and inexplicable. (Viveka-cūḍāmaṇi 111)

Learn more: The Vaiṣṇava Concept of Māyā

Śrīla Raghunātha dāsa Gosvāmī compared impersonal liberation to a tigress that devours the self: “My dear mind, never listen to talk about impersonal liberation, which is like a tigress that swallows everything, including the self ” (kathāḥ mukti-vyāghryā na śṛṇu kila sarvātma-gilanīḥ, Manaḥ-śikṣā 4).

Śrī Caitanya Mahāprabhu also sternly warned those who aspire to know Bhagavān in truth: “If one hears the Advaitavāda interpretation everything comes to ruin” (Caitanya-caritāmṛta, Madhyalīlā 6.153). Ultimately, He explained, because the Advaitavādīs strip Absolute Reality of its inherent aesthetic value, distinctiveness, and power, they are the greatest offenders against Svayaṁ Bhagavān, Śrī Kṛṣṇa.