Mandukya Upanishad

One of the speculative religious texts
known as the Upanishads, which form
the latest stratum of the Vedas, the oldest Hindu sacred texts. The Mandukya
Upanishad’s underlying concern is to
investigate ultimate questions, in particular the nature of the Self (atman). The
Mandukya Upanishad is generally considered one of the latest upanishads,
based on its brevity—a mere twelve
verses—and on its concise articulation
of philosophical monism. The first verse
praises the sound Om, calling it the
essence of the entire universe. The second verse identifies the world with
Brahman, the Self (atman) with
Brahman, and characterizes the Self as
having four quarters. The succeeding
verses describe the four quarters of the
Self, each of which removes another
layer of egoism: The first layer is
described as waking consciousness,
characterized by perceptions of subject
and object; the next is dream sleep,
which is sheer subjectivity; then deep
sleep, which has neither subject nor
object; and finally a mysterious state
simply called “the fourth” (turiya),
which is the Self itself.
Further verses identify these first
three states as corresponding to the
three parts of the sound Om: the vowels
“a” and “u” (which combine to form the
vowel “o”), and the letter “m.” The fourth
state is said to be “beyond all letters”
and without duality. The upanishad
explicitly states that to know this brings
one final liberation, in which one spontaneously merges with the Self.