Turiya is a Sanskrit word which simply means “The Fourth”. The origin of all this Turiya discussion started when Acharya Gaudapada used this word in his commentary of Mandukya Upanishad, Mandukya Upanishad Karika Samhita. Although in the original Mandukya Upanishad, the word used is Chaturtha, which again means “The Fourth”, Acharya Gaudapada used the word Turiya in his commentary.
Turiya is not a name given to any substance by which we are all made up of. It is just a pointer to the the explainable I.
There are 12 verses in Mandukya Upanishad which are divided as follows:
Verses 1,2: Talks about The absolute in general.
Verses 3,4,5,6,7: Talks about four aspects of Atman.
Verses 8,9,10,11,12: Again talks about aspects of Atman but on the basis of word ‘OM’.
The four aspects of Atman( or ‘I’) talked in the Mandukya Upanishad are: Waking State, Dream State, State of deep sleep and Turiya. Turiya is explained in the 7th verse as below.
Verse in Sanskrit:
नान्तःप्रज्ञं, न बहिष्प्रज्ञं, नोभयतःप्रज्ञं, न प्रज्ञानघनं न प्रज्ञं नाप्रज्ञम् । अदृष्टमव्यवहार्यमग्राह्यमलक्षणंअचिन्त्यमव्यपदेश्यमेकात्मप्रत्ययसारं
प्रपञ्चोपशमं शान्तं शिवमद्वैतं चतुर्थं मन्यन्ते स आत्मा स विज्ञेयः ॥
The verse has three modes. One modes talks in term of negation. Meaning, it describes Who I am not. Second mode talks in terms of attributive assertion describing Who I am. Third is the conclusive mode.
Who ‘I’ am Not:
The self(‘I’) is Not inward turned consciousness (Na antah prajnam). This is referred to dreaming state of the me. I is Not outward turned consciousness (Na bahish prajnam). This is referred to waking state of person. I is Not in-between consciousness (nobhaya antah prajnam). This is referred to as state between dreaming and waking. I is Not undifferentiated consciousness (Na prajnana ghanam). This refers to state of deep sleep.I is Not any knowing(na prajnam) and Not unknowing(na aprajnam).
Who ‘I’ am:
The self(‘I’) is Adrishtam(Invisible or not a subject of our five senses), avyavaharayam ( Not releated or transactionable ), agrahyam (Ungraspable, Incomprehensible), alakshanam (without any characteristics: hence can’t be inferred), achintyam(Inconceivable, can’t think about it), avyapadesyam (Indefinable, can’t be named), prapanch opasarnam(unreleated to the existence), shantam(Absolutely Slient), shivam (Absolutely Blissful), advaitam(Non-dual: One and only existence).Its sole essence being the consciousness/feeling of its own Self (eka atma pratyaya saram).
Thought as the fourth(chaturtha manyante): which inferentially means that it is not the fourth, not separate from other three states, sa Atman (That is ‘I’: me, The Self), sa vijneyah (That has to be to realized).
**********Explanation ends here.**********
Notice that we used the word ‘Self’ as third object like What Self is or what self is not. But we were not discussing about The Self . We were discussing about ‘I’. This is usual mistake when we try to understand the subjective feeling in objective manner.
Replace the word The Self is this or that(Objective) by I am this or that(Subjective), you can easily relate it to the words of Krishna in Bhagwad Geeta which is a subjective text.
‘I’ is not the ego asserted by relating ourself to the existence. It is the underlying truth proclaimed by Self-realized.