Acosmism, in contrast to pantheism, denies the reality of the universe, seeing it as ultimately illusory, (the prefix "a-" in Greek meaning negation; like "un-" in English), and only the infinite unmanifest Absolute as real. Conceptual versions of Acosmism are found in eastern and western philosophies.
The concept of Maya in non-dual Advaita Vedanta school of Hinduism is a form of acosmism. Maya means "illusion, appearances". The universe is considered to be Māyā, however this does not mean universe is considered as unreal. Wendy Doniger explains, "to say that the universe is an illusion (māyā) is not to say that it is unreal; it is to say, instead, that it is not what it seems to be, that it is something constantly being made. Māyā not only deceives people about the things they think they know; more basically, it limits their knowledge to things that are epistemologically and ontologically second-rate."
In Vedanta school of Hinduism, cosmos is a Maya that hides the Absolute and Ultimate Reality (Brahman). Human mind constructs a subjective experience, states Vedanta school, which leads to the peril of misunderstanding Maya as well as interpreting Maya as the only and final reality. Vedantins assert the "perceived world including people are not what they appear to be, there is more to them that their perceived physical forms". There are invisible principles and laws at work in cosmos and in individuals, assert Vedanta scholars, true nature in others and objects that is invisible, and this invisible soul that one never perceives directly, but this invisible reality of spiritual Atman (Self, Soul) exists. Māyā is that which manifests, perpetuates a sense of false duality (or divisional plurality). This manifestation is real, but it obfuscates and eludes the hidden principles and true nature of reality. Vedanta school holds that liberation is the unfettered realization and understanding of these invisible principles – the Self, that the Self (Soul) in oneself is same as the Self in another and the Self in everything (Brahman).
Advaita Vedanta school is best described as monistic, absolute idealism, while Dvaita Vedanta school as pluralistic idealism. Both have elements of ontological acosmism, where the material aspect of cosmos is considered an "illusion, appearance, incomplete reality" in that "which is spiritual, eternal, unchanging" sense. In Advaita Vedanta philosophy, there are two realities: Vyavaharika (empirical reality) and Paramarthika (absolute, spiritual reality). Māyā is a fact in that it is the appearance of phenomena. Brahman (Ultimate Reality, Absolute, Cosmic Soul) is held by Advaitins as the metaphysical truth. The perceived world, Māyā is true in epistemological and empirical sense; however, Māyā is not considered by Vedantins as the metaphysical and spiritual truth. The spiritual truth is the truth forever, while what is empirical truth is only true for now. Since Māyā is the perceived material world, it is true in perception context, but is "untrue" in spiritual context of Brahman. True Reality, to Advaita scholars, includes both Vyavaharika (empirical) and Paramarthika (spiritual), the Māyā and the Brahman. The goal of spiritual enlightenment, state Advaitins, is to realize one's soul as same as Cosmic Soul (Brahman), realize the eternal, fearless, resplendent Oneness.