The Indian tradition refers to the Mandukya Upanishad, verse 7 to describe the Fourth State, or Fourth Condition, or Fourth Quarter of Consciousness named Turiya. In the interpretation made by Shankara, the founder of the Advaita (Nondualism or Monism) Turiya is Atman or the Soul.

In my analysis, the Fourth Quarter of Consciousness is the Seat of Consciousness where the Contents of the Consciousness are assembled or Composed to account for the Capacity of Consciousness. While the Indian Tradition describes the Fourth Quarter as ATMAN (the True or Real Self), I name it as The Knowing-Self to make the distinction between the Self (Body and Mind) and the Soul. In making the distinction between the Self (Body and Mind) and the Atman or the Soul, I follow the argument proposed by Shankara in his poem the Nirvana Shatakam or Atma Shatakam.

To further describe the Soul, The Knowing-Self, or ATMAN, I will ask my readers to explore the Functional Anatomy of Reticular Formation of the Brainstem. In my view, the ATMAN/SOUL/THE KNOWING-SELF is the substratum associated with the Functional Capacity of Consciousness. Indian thinkers like Shankara and various others account for the information processed by the cerebral cortex of the brain or the cortical awareness as consciousness and are ignorant of the functional anatomy of the Reticular Formation of the Brainstem where the contents of consciousness are actually assembled or composed.

For example, the human subject who recognizes the fourth quarter or Turiya is always cognizant of the position of his body in space to maintain the postural orientation, postural balance, postural equilibrium, and postural control associated with various dynamic and static activities such as sitting, standing, or running. The man involved in the practices of YOGA such as Dhyana, Meditation, and Samadhi has to still maintain his Asana or Bodily Posture.

Mandukya Upanishad: Translation by Jayaram V

The Mandukya Upanishad belongs to the Atharvaveda. Although it contains only 12 verses, the Mandukya Upanishad occupies an important place in the development of Indian philosophical thought, following a commentary or Karika on it by Gaudapada, who is believed to be a teacher of Adi Shankaracharya.

Gaudapada Karika on the Upanishad became the basis for the emergence of the Advaita Vedanta or the philosophy of monism, according to which Brahman alone is the truth and the rest is an illusion. The Upanishad deals with the symbolic significance of the sacred syllable Aum and its correlation with the four states of consciousness, namely the wakeful consciousness, dream state, the state of deep sleep or dreamless sleep and the state of transcendental consciousness in which all divisions and duality disappear and the self alone exists in its pure state, all by itself.

1. This syllable AUM is verily all this
This is the explanation about AUM:
The past, the present and the future are AUM,
And That beyond these three is also AUM.

2. Brahman is indeed all this.
This self in us is also Brahman.
And this self has four planes.

3. Vaisvanara is the first stage.
Wakeful, outwardly conscious,
With seven limbs and nineteen mouths,
He is the enjoyer of the gross objects.

4. Taijasa is the second stage.
Dreaming, inwardly conscious,
With seven limbs and nineteen mouths,
He is the enjoyer of the subtle objects.

5. In deep sleep, seeking no desires,
Dreaming no dreams, unified into
The mass of greater consciousness,
Full of bliss, enjoying bliss only,
Face turned towards Chetasa,
Is Prajna the third stage.

6. This is the Master of All, the Omniscient,
The Inmost Dweller and source of
Creation and destruction of all beings.

7. Conscious, not internally not externally,
Nor either ways, neither ordinary consciousness,
Nor the greater and the deeper consciousness,
Invisible, otherworldly, incomprehensible,
Without qualities, beyond all thoughts,
Indescribable, the unified soul in essence,
Peaceful, auspicious, without duality,
Is the fourth stage, that self, that is to be known.

8. The same Atman is AUM among the syllables,
Each syllable in the word AUM is a stage. They
Are the letter A, the letter U and the letter M.

9. The wakeful Vaishwanara is the
First letter “A”, being the first letter and
All pervasive. He who knows thus realizes
All his desires and becomes foremost too.

10. The dreaming Taijasa is the second
Letter “U”, being superior and situated in
The middle. He who knows thus attains
Knowledge and children equally and none
In his family would be ignorant of Brahman

11. In the world of deep sleep, Prajna, is the
Third letter “M”, being the limit and the end of
All diversity. He who knows thus is free from
All diversity and becomes one with the Self.

12. The fourth state is without parts and entanglements
Not bound to this world, It is auspicious and non-dual
Thus the form of AUM is verily the Self itself
He who knows thus enters into his own Self by himself.

Mandukya Upanishad, seventh verse:

नान्तःप्रज्ञं न बहिःप्रज्ञं नोभयतःप्रज्ञं न प्रज्ञानघनं न प्रज्ञं नाप्रज्ञम् | अदृश्यमव्यवहार्यमग्राह्यमलक्षणमचिन्त्यमव्यपदेश्यमेकात्मप्रत्ययसारं प्रपञ्चोपशमं शान्तं शिवमद्वैतं चतुर्थं मन्यन्ते स आत्मा स विज्ञेयः || 7 ||

nāntaḥprajñaṃ na bahiḥprajñaṃ nobhayataḥprajñaṃ na prajñānaghanaṃ na prajñaṃ nāprajñam | adṛśyamavyavahāryamagrāhyamalakṣaṇamacintyamavyapadeśyamekātmapratyayasāraṃ prapañcopaśamaṃ śāntaṃ śivamadvaitaṃ caturthaṃ manyante sa ātmā sa vijñeyaḥ || 7 ||

7. Turīya is not that which is conscious of the internal (subjective) world, nor that which is conscious of the external (objective) world, nor that which is conscious of both, nor that which is a mass all sentiency, nor that which is simple consciousness, nor that which is insentient. (It is) unseen (by any sense organ), not related to anything, incomprehensible (by the mind), uninferable, unthinkable, indescribable, essentially of the nature of Consciousness constituting the Self alone, negation of all phenomena, the Peaceful, all Bliss and the Non-dual. This is what is known as the fourth (Turīya). This is the Ātman and it has to be realised.

      (‘Consciousness’ as the nearest English word is used.)

Shankara Bhashya (commentary)

(Objection)—The object was to describe Ātman as having four quarters. By the very descriptions of the three quarters, the fourth is established as being other than the three characterised by the “conscious of the subjective”, etc. Therefore the negation (of attributes relating to the three quarters) for the purpose of indicating Turīya implied in the statement, “Turīya is that which is not conscious of the subjective”, etc., is futile.

(Reply)—No. As the nature of the rope is¹ realised by the negation of the (illusory) appearances of the snake, etc., so also it is intended to establish the very Self, which subsists in the three states, as Turīya. This² is done in the same way as (the great Vedic statement) “Thou art that”. If Turīya were, in fact, anything different³ from Ātman subsisting in the three states, then, the teachings of the Scriptures would have no meaning on⁴ account of the absence of any instrument of knowledge (regarding Turīya). Or the other (inevitable alternative would be to declare absolute nihilism ( śūnya) to be the ultimate Truth. Like the (same) rope mistaken as snake, garland, etc., when the same Ātman is mistaken as Antaḥprajña (conscious of the subjective) etc., in the three states associated with different characteristics, the knowledge, resulting from the negation of such attributes as the conscious of the subjective, etc., is the means of establishing the absolute absence of the unreal phenomena of the world (imagined) in Ātman. As a matter of fact, the two⁵ results, namely, the negation of (superimposed) attributes and the disappearance of the unreal phenomena happen at the same time. Therefore no additional⁶ instrument of knowledge or no other⁷ effort is to be made or sought after for the realisation of Turīya. With the cessation of the idea of the snake, etc., in the rope, the real nature of the rope becomes revealed and this happens simultaneously with the knowledge of the distinction between the rope and the snake. But those who say that the knowledge, in addition to the removal of the darkness (that envelopes the jar), enables⁸ one to know the jar, may as well affirm⁹ that the act of cutting (a tree), in addition to its undoing the relation of the members of the body intended to be cut, also functions (in other ways) in other parts of the body. As the act of cutting intended to divide the tree into two is said to be complete with the severance of the parts (of the tree) so also the knowledge employed to perceive the jar covered by the darkness (that envelopes it) attains its purpose when it results in removing the darkness, though that is not the object intended to be produced. In such case the knowledge of the jar, which is invariably¹⁰ connected with the removal of the darkness, is not the result accomplished by the instrument of knowledge. Likewise, the knowledge, which is (here) the same as that which results from the negation of predicates, directed towards the discrimination of such attributes as “the conscious of the subjective” etc., superimposed upon Ātman, cannot¹¹ function with regard to Turīya in addition to its act of negating of such attributes as “the conscious of the subjective” which is not the object intended to be produced. For, with the negation of the attributes such as “conscious of the subjective,” etc., is¹² accomplished simultaneously the cessation of the distinction between the knower, the known and the knowledge. Thus it will be said later on, “Duality cannot exist when Gnosis, the highest Truth (non-duality), is realised.” The knowledge of duality cannot exist even for a moment immediately after the moment of the cessation of duality. If it should remain, there would^13; follow what is known as regressus ad infinitum; and consequently duality will never cease. Therefore it is established that the cessation of such unreal attributes as “conscious of the subjective” etc., superimposed upon Ātman is¹⁴ simultaneous with the manifestation of the Knowledge which, in itself, is the means (pramāṇa) for the negation of duality.

By the statement that it (Turīya) is “not conscious of the subjective” is indicated that it is not “Taijasa”. Similarly by the statement that it is “not conscious of the objective,” it is denied that it (Turīya) is Viśva. By saying that it is “not conscious of either”, it is denied that Turīya is any intermediate state between¹⁵ the waking and the dream states. By the statement that Turīya is “not a mass all sentiency”, it is denied that it is the condition of deep sleep—which is held to be a causal¹⁶ condition on account of one’s inability to distinguish the truth from error (in deep sleep). By saying that it is “not simple consciousness”, it is implied that Turīya cannot¹⁷ simultaneously cognize the entire world of consciousness (by a single act of consciousness). And lastly by the statement that it is “not unconsciousness” it is implied that Turīya is not insentient or of the nature of matter.

(Objection)—How,¹⁸ again, do such attributes as “conscious of the subjective,” etc., which are (directly) perceived to subsist in Ātman become non-existent only by an act of negation as the snake, etc. (perceived) in the rope, etc., become non-existent (by means of an act of negation)?

(Reply)—Though¹⁹ the states (waking and dream) are really of the essence of consciousness itself, and as such are non-different from each other (from the point of view of the substratum), yet one state is seen to change²⁰ into another as do the appearances of the snake, water-line, etc., having for their substratum the rope, etc. But the consciousness itself is real because it never changes.

(Objection)—Consciousness is seen to change (disappear) in deep sleep.

(Reply)—No, the state of deep sleep is a matter of experience.²¹ For the Śruti says, “Knowledge of the Knower is never absent.”

Hence it (Turīya) is “unseen”²²; and because it is unseen therefore it is “incomprehensible”.²³ Turīya cannot be apprehended by the organs of action. Alakṣanam means “uninferable”,²⁴ because there is no Liṅga (common characteristic) for its inference. Therefore Turīya is “unthinkable”²⁵ and hence “indescribable”²⁶ (by words). It is “essentially²⁷ of the nature of consciousness consisting of Self”. Turīya should be known by spotting that consciousness that never changes in the three states, viz., waking, etc., and whose nature is that of a Unitary Self. Or,²⁸ the phrase may signify that the knowledge of the one Ātman alone is the means for realising Turīya, and therefore Turīya is the essence of this consciousness or Self or Ātman. The Śruti also says, “It should be meditated upon as Ātman.” Several attributes, such as the “conscious of the subjective” etc., associated with the manifestation (such as, Viśva, etc.) in each of the states have already been negated. Now by describing Turīya as “the cessation of illusion”, the attributes which characterise the-three states, viz., waking, etc., are negated. Hence it is “ever²⁹ Peaceful”, i.e., without any manifestation of change—and “all³⁰ bliss”. As it is non-dual, i.e., devoid of illusory ideas of distinction, therefore it is called “Turīya”, the “Fourth”,³¹ because it is totally distinct (in character) from the three quarters which’ are mere appearances. “This, indeed, is the Ātman and it should be known,” is intended to show that the meaning of the Vedic statement, “That thou art”, points to the relationless Ātman (Turīya) which is like the rope (in the illustration) different from the snake, line on the ground, stick, etc,, which are mere appearances. That Ātman which has been described in such Śruti passages as “unseen, but the seer”, “the consciousness of the seer is never absent”, etc., should be known. (The incomprehensible) Turīya “should be known”, and this³² is said so only from the standpoint of the previously unknown condition, for duality cannot exist when the Highest Truth is known.

Anandagiri Tika (glossary)

¹ Is realised—The rope did not cease to be the rope when it appeared as the snake. The rope, again, is seen in its true nature when the snake idea is removed. Similarly, Ātman appears as Viśva, Taijasa and Prājña in the three states. And the same Ātman is realised as Turīya when the upādhis, namely the states, are negated. Turīya is not a separate entity nor is it a fourth state succeeding the three other states. The real nature of Turīya cannot be realised without the negation of the upādhis of the three states.

² This is, etc.—The real significance of “That thou art”, is Turīya and it is realised when the contrary qualities, known as the upādhis, indicated by the words “That” and “thou” are eliminated. Similarly, the Scripture by the negative process, removes the upādhis of the Ātman when associated with the three states and this reveals its eternal identity with Turīya.

³ Different—From the relative or causal standpoint, the Ātman associated with any of the three states, is, no doubt, different from Turīya. But from the standpoint of Turīya there is no difference whatsoever between it and the Ātman associated with the three states. As a matter of fact, it is Turīya as the witness (sākṣi) that is revealed out by the three states.

⁴ On account of— Ignorant person, for whom Scripture is prescribed for the attainment of Knowledge, moves in the relative plane of the three states. To him the Scripture suggests the examination of the three states in order to arrive at the Knowledge of Turīya. If Turīya were something totally separate from and essentially unconnected with the three states and if the three states were not the means of realising Turīya, then no other instrument of Knowledge would be left for the realisation of Turīya. It cannot be contended that one can get the Knowledge of Turīya from the Scripture. Because the Scripture also teaches about Turīya by the method of repudiation (apavāda) of the superimposed attributes (adhyāropa) by negating the upādhis which were superimposed upon Turīya. If Turīya were something totally different from the three states, then no scriptural teaching would be effective in establishing it. If Turīya cannot be established through the examination of the Ātman qualified by the three states, by following the scriptural method of negation, then one is faced with the only alternative that the Ultimate Reality is total non-existence (śūnya) because no other reality remains after the negation of the upādhis of the three states if the existence of Turīya be denied.

⁵ Two results—The instrument of Knowledge (pramāṇa) by means of which we become aware of the result of the negation of the upādhis, namely, the three states, reveals the relationless Turīya. It is like the seeing of the real rope (which is never absent) with the cessation of the illusory idea of the snake. It must be carefully noted that the realisation of Turīya is not the result of the Pramāṇa by means of which we become aware of the negation of the attributes of Ātman, viz., the three states. The two results are simultaneous—and not successive in time as the language seems to imply. It is because no new entity known as Turīya is discovered (or comes into existence) after the negation of upādhis. Turīya is always present. Therefore there īs no possibility of taking Turīya as the result of the negation of the upādhis, viz., the three states. Turīya b eing characterised by non-duality there is no subject-object relationship m Turīya in which case alone an instrument of Knowledge would have a meaning.

⁶ Additional instrument, etc.—No instrument of Knowledge can establish Turīya on account of its non-relation and non-dual nature. Even the function of the Śruti which indicates Turīya is only to negate what is unreal, relative and non-Brahman.

⁷ Other effort—Even contemplation, etc., which are the essential features of Yoga cannot establish Turīya, because it cannot be proved that Yogic contemplation can yield such Knowledge. Therefore the realisation of Turīya cannot be characterised as the result of any particular instrument of Knowledge or of any Yogic practice.

⁸ Enables, etc.—This means that the instrument of Knowledge, besides removing the darkness enveloping the Jar, also yields another positive result that is the manifestation of the Jar.

⁹ Affirm—This means that the act of cutting besides severing the parts to which it is directed also functions in other ways. But this is absurd because we have no knowledge of any other effect op the tree produced by the act of cutting.

¹⁰ Invariably, etc.—It is because the Jar always exists even when it is enveloped in darkness.

¹¹ Cannot function.— It is because Turīya is Knowledge itself. Hence no instrument of Knowledge can act upon it. Turīya does not stand in need of any demonstration or proof because it is ever-existent. The instrument of Knowledge only removed the super-impositions falsely attributed to Ātman. The instrument of Knowledge (perception) continues to act upon an object till the object is revealed (as Brahman).

¹² Is accomplished— The instrument of Knowledge, invariably connected with its employer and an object, can act only in the plane of duality. With the negation of duality, the instrument of Knowledge itself becomes ineffective, for it cannot function the next moment. The idea of time is also annihilated with the destruction of duality. When the non-dual Turīya is realised, all ideas of the instrument of Knowledge, the employer and the object with their distinction are destroyed. Only Brahman is.

¹³ Would follow, etc—It is because a second instrument of Knowledge would be required to negate the residual Knowledge or instrument and a third would be necessary to negate the second and so on ad infinitum. An argument ending in a regressus is not allowed in logical discussion.

¹⁴ Is simultaneous—Here Pramāṇa is the Jñānam that results from the negation of attributes. And through this instrument of Knowledge alone we know that all relative ideas have been negated.. Simultaneously with this assurance, Turīya is realised.

¹⁵ intermediate, etc.—It is the state when one experiences something like a “day dream” that is, he half sees the one and half sees the other.

¹⁶ Causal condition—By seeing the manifestation in the waking state one naturally infers that the preceding state, that is Suṣupti, is the cause of both the waking and dream experiences. In Suṣupti, specific states of consciousness, which manifest themselves as different objects in dream and waking states, remain in a state of indistinguiṣability. In deep sleep, no distinctions are perceived.

¹⁷ Cannot, etc.—By this are denied such attributes as omniscience, etc., associated with Īśvara.

¹⁸ How, etc.—The contention of the objector is this: That the idea of the snake, etc., in the rope is an illusion is a matter of’ common experience. When the error is pointed out, the idea of the snake disappears. Therefore the idea of such a snake can be said to be non-existent. But this is not the case with the attributes of Ātman which are sought to be negated. Such attributes are directly perceived by everyone and do not vanish even though they are negated. Therefore the phenomena of the three states cannot be said to be non-existent on the analogy of the rope and the snake.

¹⁹ Though, etc.—The reply is that the attributes, viz., the three-states, can be demonstrated to be non-existent (unreal) by the act of negation. The illustration of the snake and the rope is quite-apposite. The ideas of the snake, the water-line, etc., for which the rope is mistaken are first pointed out to be illusion because, they are subject to change. Therefore, such objects as are indicated by the ideas are non-existent. Similarly it is a matter or common experience that the states of Jāgrat, Svapna and Suṣupti are subject to change. Therefore they are negatable. In any one state the two other states are negated. Besides, in the state of waking one can realise the three states as following one another. Therefore the three states partake of the nature of unreality as distinguished from Reality which is never subject to any change. Now, what is Reality? From the examination of the three states it becomes clear that though the states are changing and negatable the consciousness which is present therein is constant and invariable. Change of one state to another cannot affect the unchanging nature of Consciousness itself. Therefore pure Consciousness is real. Hence it follows that by constantly examining the changeable and negatable character of the attributes, viz., the three states, one can realise their non-existent or unreal nature. The fallacy of the contention of the objector is due to the partial examination of Reality in only one state in which case the changeable nature of the attributes cannot be realized. But the examination of the three states at once demonstrates their changeable and negatable nature and points out that consciousness itself which is the sub* stratum of the changing attributes is the only Reality.

²⁰ Change—That is, no one is aware of consciousness in deep sleep.

²¹ Experience—Consciousness cannot be dissociated from the state of deep sleep. Suṣupti is experienced from the Jāgrat state, that is to say, Turīya in Jāgrat state knows that it experienced deep sleep. Otherwise Suṣupti would have never been known to exist at all.

²² Unseen—It cannot be recognised by any organ of perception. It is because Turīya is the negation of all the attributes. It cannot be made the object of any sense-organ.

²³ incomprehensible—It cannot come within the cognizance of the senses: therefore Turīya cannot serve any purpose (arthakiyā??).

²⁴ Uninferable—“Existence, Knowledge and Infinity,” by which Brahman is described in the Taittirīya Upaniṣad are not to be considered to be real and positive attributes for the purpose of drawing an inference about Brahman. They only serve a negative purpose indicating that Brahman is other than non-truth, nonconsciousness and non-infinity. Besides, inference requires a common feature which always presupposes more objects than one. But Brahman is one and without a second. Therefore no inference is possible regarding Brahmān.

²⁶ Unthinkable—It is because the predicates by which we can think about an entity have been totally eliminated from Turīya.

²⁸ Indescribable—Turīya cannot be described by words because it is unthinkable. That which one thinks in mind, is expressed by words.

²⁷ Essentially, etc.—The elimination of all the attributes may make Turīya appear as a void to the unwary student. Therefore it is described as a positive existence which can be realised by spotting it as the changeless and the constant factor in the three states. The states, no doubt, do change but there is a unity of the subject implied in the conscious experience of “I am that perceiver” common to all the three states.

²⁸ Or—The alternative meaning is that through consciousness-of Self alone, which forms the basis of the three states, we can demonstrate Turīya which transcends all the states, or in other words, because there is Pure Consciousness, changeless and constant, known as Turīya, therefore we are aware of self-consciousness in the three states.

²⁹ Ever-peaceful—Free from attachment of love and hate, i.e., changeless and immutable.

³⁰ All Bliss—Pure and embodiment of the highest Bliss.

³¹ Fourth—This does not signify any numerical relationship-with the three other states narrated previously. Turīya is called the “fourth” because it occupies the “fourth” place in order of explanation of Brahman of which the three states have previously been dealt with.

³² This is, etc—The statement that “It should be known cannot be properly made with regard to the non-dual Ātman which is incomprehensible, etc. This objection is, no doubt, valid from, the standpoint of Turīya where there cannot be a separate knower of Ātman. But Turīya is certainly unknown from the standpoint of any of the three states, and from that dual standpoint it is perfectly legitimate to speak of Brahman as something “to be known.”

Frontiers of Psychology., 07 August 2020 | https://doi.org/10.3389/fpsyg.2020.01992

Consciousness Without Content: A Look at Evidence and Prospects

Narayanan Srinivasan^1,2*

• ¹Centre of Behavioural and Cognitive Sciences, University of Allahabad, Allahabad, India
• ²Interdisciplinary Program in Cognitive Science, Indian Institute of Technology Kanpur, Kanpur, India

Many traditions in the East have proposed that consciousness without content is possible and could be achieved with mental training. However, it is not clear whether such a state is possible given that intentionality is a critical property of mentality and consciousness in many theories of consciousness. A prominent recent attempt to account for such states of “minimal phenomenal experience” is the ascending reticular arousal system (ARAS) model, which proposes a specific type of non-conceptual representational content to address such a state. Consciousness without content can also be understood by studying related or similar states of minimal phenomenal experience and this paper discusses such findings from such states including dreamless sleep experience and their implications. One way to argue for the need for proposing consciousness without content is to locate a property of consciousness that would necessitate postulating it. A continuous state of consciousness without content may be needed to understand continuity of conscious experience. Finally, I discuss the implications of consciousness without content for current theories of consciousness.

Introduction

Multiple contemplative traditions report exceptional experiences and these experiences pose critical questions for the study of consciousness (Thompson, 2014; Metzinger, 2019). These exceptional experiences have been used to characterize and define states of consciousness. One of the earliest writings on states of consciousness comes from the Upanishads (Olivelle, 1998; Thompson, 2014). Verse 7 of the Mandukya Upanishad mentions four states of consciousness. Three states of consciousness are familiar, which are wakefulness, dreaming, and sleep. The most interesting and unusual is the fourth state called Turiya. Turiya is defined as follows: “They consider the fourth quarter as perceiving neither what is inside nor what is outside, nor even both together; not as a mass of perception, neither as perceiving nor as not perceiving; as unseen; as beyond the reach of ordinary transaction; as ungraspable; as without distinguishing marks; as unthinkable; as indescribable; as one whose essence is the perception of itself alone; as the cessation of the visible world; as tranquil; as auspicious; as without a second. That is the self (atman), and it is that which should be perceived (Olivelle, 1998, p. 475).” Turiya is also mentioned in other Upanishads as well; for example, in Brihadaranyaka Upanishad, chapter 5.14.3 (Olivelle, 1998). Turiya is not simply another state of consciousness but is considered the basis of all the other three states of consciousness. Given this conceptualization, the possibility of Turiya has important implications for theories of consciousness (Metzinger, 2019).

A variation of the concept of Turiya can be found in Kashmir Shaivism (Lakshmanjoo, 2015, 2017). According to this, there is a junction between each of three states, wakefulness, dreaming, and deep sleep. Turiya can be experienced in these junctions with practice. Some minor Upanishads and Kashmir Shaivism also propose a fifth state of consciousness called Turiyatita, which is a state beyond Turiya. Kashmir Shaivism also talks of seven states of Turiya or bliss (Lakshmanjoo, 2017) in terms of progressive steps achieved through practice. These include nijananda (the bliss of your own self), nirananda (devoid of limited bliss), prananda (the bliss of breathing), brahmānanda (the bliss which is all-pervading), mahananda (the great bliss), cidānanda (the bliss of consciousness), and jagadānanda (universal bliss).

Buddhists also talk about different states or planes of consciousness. They mention four planes of consciousness, in which the fourth plane is called Lokuttara, which is unintentional consciousness (nirvana). Nirvana is a pure conscious state (Rao and Paranjpe, 2015). In later schools like Vajrayana, Buddha Nature (ultimate reality) is defined as permanence, bliss, purity, and self (Takasaki, 1966). The state of consciousness without content is problematic because such states are described as being non-intentional. Recent attempts to understand such states characterize non-dual consciousness in terms of multiple dimensions, which include presence or being, emptiness, non-representational reflexivity, bliss, luminosity, continuity, and singularity (Josipovic, 2019; Josipovic and Miskovic, 2020).

On a first pass, the definition of Turiya as given in the Upanishads or samadhi or nirvana seems formidable and difficult to capture by empirical methods. It is also possible that pure consciousness is conflated with absorption states like samadhi (Josipovic and Miskovic, 2020). So, the first question ignoring the difficulties posed by the definition is whether Turiya exists. If it does not exist (as defined?), then how do we understand the Turiya experience and how do we explain it? This paper will discuss one such prominent attempt, which is the ascending reticular arousal system (ARAS) model by Metzinger (2019).

If a state of consciousness without content (Turiya or Nirvana) does exist, then how do we study it? This paper sympathetically explores the possibility of consciousness without content and discusses possible ways to attack this problem. One possibility is to link it to states of consciousness or minimal phenomenal experience that are close in nature, study them, and interpolate (Baars, 2013; Windt, 2015). The second possibility is to argue for a need to postulate consciousness without content to explain specific properties of consciousness. In this paper, I will focus on the continuity of conscious experience and whether this necessitates postulation of consciousness without content, primarily based on Buddhist theories of consciousness. Finally, I will discuss current scientific theories in the context of consciousness without content.

A Model of Minimal Phenomenal Experience (MPE)

The nature of consciousness and its phenomenal properties have also been investigated in western philosophy (Tye, 1997). For example, Metzinger (2019) quotes from Moore (1903) regarding transparency: “the moment we try to fix our attention upon consciousness and to see what, distinctly, it is, it seems to vanish: it seems as if we had before us a mere emptiness. When we try to introspect the sensation of blue, all we can see is the blue: the other element is as if it were diaphanous (Moore, 1903, p. 450).” The argument is that we can access only content but not content-carrying vehicle properties. Consciousness without content is not possible and consciousness is a second-order process. The second-order meta-awareness is generally not noticed but can be noticed through attention.

Based on phenomenological reports and analysis, Metzinger (2019, 2020) postulates certain phenomenological constraints for the minimal phenomenal experience (MPE). They are tonic alertness, absence of intentional content or content of “absence,” self-luminosity, introspective availability, epistemicity, and transparency. A state of full absorption is mostly characterized by wakefulness and self-luminosity. Lucid dreamless sleep is also somewhat similar to the state of full absorption, which is discussed in the next section.

Metzinger (2019) defines the minimal form of experience as: “constituted by the content of a predictive model serving to control and regulate the global signal of the ARAS, which in turn determines the brain’s general level of activation (pp. 1).” The model argues that this minimal phenomenal experience appears to be empty because it models a hidden cause of the ARAS signal, which is non-intentional vehicle property. The choice of the ARAS is due to its strength and its non-representational nature and this system needs to be controlled to obtain optimal level of arousal. While the ARAS signal itself is continuous, the ARAS model is discrete. In Metzinger (2020), the minimal phenomenal experience is defined in terms of a representation of tonic alertness maintained by the cingulo-opercular network (Sadaghiani and D’Esposito, 2015).

The model in essence argues that content-less consciousness is an illusion and the pure consciousness state actually has non-conceptual representational content. To be more specific, the model argues that the non-conceptual content is “empty” or “non-representational.” The “content-less” phenomenal state actually carries an abstract form of intentional content. Metzinger (2019, 2020) raises questions about taking the phenomenological reports as they are in terms of no-content. If it is the case that there is no sense of self or time, how could one remember that one was in such a state sans content or remember the duration or onset of such a state? In addition, it points to the fact that the experience and its report could be affected by the expectations and theories associated with such experiences in various contemplative traditions.

States Close to Consciousness Without Content

Irrespective of whether the state of consciousness without content is actually without content or a special content (Metzinger, 2019), it is important to study such a state or reported experiences of such a state. Whether truly consciousness without content is possible or not, some have suggested focusing on states with minimal content as a way to get closer to reported experiences of such non-content states (Baars, 2013). Such suggestions include experiences based on repetition including Ganzfeld experiences and near threshold attending (Baars, 2013).

One possible way to study them would be to study neural measures associated with such a state with meditators who claim to experience such states (Hinterberger et al., 2014). In this electroencephalogram (EEG) study with experienced meditators, participants were asked to perform different types of meditation, which included thoughtless emptiness, focused attention, and open monitoring. Results showed that thoughtless emptiness is characterized not just by reduction in power of high frequencies but also low frequencies in EEG. In a more recent study (Winter et al., 2020) with a single experienced Buddhist meditator, conscious state without content was reported toward the end of the meditation session. EEG results showed a reduction in alpha power and increase in theta power during the self-reported content-free awareness period compared to the rest. The functional connectivity results showed decreases in the posterior default mode network and increases in connectivity in the dorsal anterior network. A direct comparison of the EEG results from the two studies show that the spectral analysis results do not confirm with each indicating the potential difficulties with studying such a state using EEG at present.

Some neural areas or systems have been proposed to underlie MPE states (Baars, 2013; Hinterberger et al., 2014; Josipovic, 2019). One proposal is the central precuneus network (Josipovic, 2014, 2019), which shows increased connectivity between central precuneus and the dorsolateral prefrontal cortex and could underlie nondual awareness. Another neural measure that has been proposed for minimal phenomenal experience is larger theta-alpha power perhaps accompanied by much reduced power in beta or gamma frequency ranges (Baars, 2013). Studies on sensory deprivation have also been used to study MPE states (Ben-Soussan et al., 2019) and insula has been proposed an important area for such states. However, there is very little conclusive evidence for neural mechanisms that underlie such states at the current juncture. It is also not clear whether these states have anything in common, which can also be discerned from the different neural substrates proposed in different studies (Baars, 2013; Hinterberger et al., 2014; Josipovic, 2014).

Dreamless Sleep Experience

Windt (2015) proposes that “dreamless sleep experience can be described as pure temporal experience (pp. 35)” and could be considered a minimal phenomenal experience. In this state of dreamless sleep experience, there is experience of time but without any intentional content. The nature of dreamless sleep has been debated among different Indian philosophical systems (Thompson, 2014; Windt, 2015). Different Indian philosophical systems allow or disallow cognitive states without content. For example, the Nyaya does not allow objectless cognitive states but Advaita does. A state of consciousness without content or a pure temporal experience without content is possible according to Advaita. Given that pure self or consciousness is always present, Advaita argues that consciousness is present during dreamless sleep.

During such a dreamless sleep experience, the experience is that of a no-self and no intentional content. Windt (2015) argues that this experience can be understood as a phenomenal “now.” Using Husserl’s notion of retention (Husserl, 1991), Thompson (2015) argues that the recognition of absence of self and intentional content can possibly be based on retentional aspects of the “now.” While acknowledging, the possibility of dreamless sleep experience as a MPE, Metzinger (2019) points out potential issues with the characterization of dreamless sleep experience. These include contentlessness, atemporality, and epistemicity. The notion of an empty phenomenal now is not clear and phenomenology of the experience of consciousness without content is that of a lack of sense of time. In addition, Windt (2015) account does not take into account “passive, non-agentive knowing,” which captures the notion of “witnessing sleep.” These considerations pointed by Metzinger (2019) are critically important for not just dreamless sleep experience but also other MPE states, both in terms of similarities and differences.

Continuity of Conscious Experience

One important debate about conscious perception is whether it is continuous or discrete (VanRullen and Koch, 2003; Dainton, 2014; Herzog et al., 2016; Fekete et al., 2018; White, 2018). It has been argued that conscious perception is discrete and the continuity of experience is as such an illusion (VanRullen and Koch, 2003; Herzog et al., 2016). Models of time perception, more specifically cinematic models assume discrete frames and imply that continuity of temporal experience is an illusion (Dainton, 2014).

Discrete models of perception generally assume that unconscious integrative processes occur over time and once the integration is complete, this results in all at once in conscious perception. This has been postulated to take around 100–500 ms. It has been argued that the conscious percept is an attractor in phase space (Herzog et al., 2016). Studies on attention have argued that attentional sampling is discrete (around 7–8 Hz) and this is a possible factor that underlies the discreteness of perception (VanRullen and Koch, 2003; VanRullen, 2016).

Arguments have been raised against the discrete model of mind or conscious perception (Spivey and Dale, 2006; Fekete et al., 2018; White, 2018). The proponents of continuous-time models of perception argue that the putative evidence for discrete perception is also consistent with continuous-time models of perception. Occasionally, the duration of the stimulus needed to consciously perceive a stimulus is conflated with the duration or timing of conscious experience (Thompson, 2014, p. 46–48).

White (2018) questions the boundaries of discrete temporal windows of momentary awareness, given that we already know that different perceptual modalities have different temporal resolutions. A gap of 30 ms may be required to segregate two flashes in foveal vision but a gap of 2–5 ms is enough to segregate two tones. In addition to temporal resolution differences across modalities, such differences also exist for different features within modalities. A classic example is the trade-off between peripheral and central vision in terms of spatio-temporal resolution. Moreover, integration of visual-auditory information themselves involve different timescales and our perceptual system can tolerate small asynchronies between the two (sounds and sight), still representing them as co-synchronous even with offsets around 50–100 ms to produce a unified audio-visual experience. White (2018) also considers the ability of such frames to explain feelings of flow, succession, and persistence of experiences beyond and within these frames. Would these problems be addressed by proposing a fourth state that is content less, non-representational, and continuous that underlie our experience?

The answer to the question of continuity (apparent or real) may have implications for the notion of consciousness without content. Different Indian systems argue for or against the continuity of consciousness (Waldron, 2003; Thompson, 2015). Many early Buddhist (Theravada and some Mahayana) theories argue for discrete moments of experience (Collins, 1982; Waldron, 2003; Thompson, 2015). However, for Buddhists, the discrete theories of consciousness do pose a problem in explaining other aspects of mind and consciousness. To quote from Evan Thompson, “How consciousness manages to function coherently, given that it is gappy. If consciousness is strictly momentary, in the sense that there is no consciousness whatsoever that persists during the gaps, then what accounts for its coherent functioning, not only from moment to moment but also across longer stretches of time? For example, what accounts for longer-lasting traits of consciousness, such as the attentional stability arising from meditation practice? Why do not the gaps between moments of awareness disrupt these continuities? (pp. 58).”

Different solutions have been proposed by different schools of Indian thought (Waldron, 2003; Thompson, 2014). The Theravada school distinguishes between active consciousness versus passive consciousness. Active consciousness is about the differing contents of experience. Here, passive consciousness is the basis of continuity of individual; “Life-continuum” or “factor of existence (bhavanga).” The passive exists only in the gaps between active (Waldron, 2003).

The Yogacara school argues for a underlying more base consciousness, which is continuously present at all time – Alaya-vijnana (store consciousness). The alaya-vijnana is the basis for cognitive awareness (which is probably discrete). This alaya-vijnana has no “I” or perspectivalness and it is the ego consciousness that brings in the “I (Waldron, 2003; Thompson, 2014).”

Sometimes bhavanga and alaya-vijnana have been interpreted as an unconscious base, which makes consciousness possible (Waldron, 2003; Rao and Paranjpe, 2015). If bhavanga or alaya-vijnana is interpreted as unconscious (but still presumably part of the mind) but continuous, then it is not clear what provides the continuity of conscious experience and it seems to simply move the problem of continuity of consciousness to continuity of non-consciousness. In addition, the term awareness or consciousness is explicitly used in many Buddhist texts in discussing bhavanga or alaya-vijnana. Alaya-vijnana is translated as storehouse consciousness and need not be interpreted as an unconscious process (Kalupahana, 1992).

Generally, Buddhist theories of time assume time to be discrete (Collins, 1982; Waldron, 2003; Thompson, 2014). Theravada assumes that bhavanga itself is discrete and made of finer moments than consciousness with content. This stance implies that even bhavanga is gappy. It has been argued with consistent meditative practice that this momentariness may become perceivable. However, even if this is true then those who meditate should report a somewhat choppy consciousness without content experience. This is not usually reported even though loss of self and time are reported (Ataria et al., 2015).

Hierarchical theories of time perception assume time scales generally in the 30–100 ms range to a few seconds range (Pöppel, 1997). If bhavanga is made of moments and then is at a scale much smaller than 30 ms range, then these moments could be even of the order of less than 1 ms. From what we know of neuronal firings and their time scales, the discrete frames for a bhavanga would require neurons firing rates that would be difficult given their physical limitations. Of course, one can argue that bhavanga as fine discrete moments is not based on neuronal activations or new finer mechanisms would emerge but at this point there are no clear possible mechanisms available at such a fine temporal scale. The hierarchical nature of time perception itself can possibly achieved with nested, synchronized activity of populations of neurons oscillating at different frequencies, which are coupled and interact with each other (Roux and Uhlhaas, 2014).

Buddhist theories, in general, do use the metaphor of the stream of consciousness and especially describe alaya-vijnana as stream. Some have used citta-santāna or mind-stream as a synonym or alternative for alaya-vijnana (Lusthaus, 2013). For example, Kalupahana (1992) says “Instead of being a completely distinct category, alaya-vijnana merely represents the normal flow of the stream of consciousness uninterrupted by the appearance of reflective self-awareness. It is no more than the unbroken stream of consciousness called the life-process referred to by the Buddha. It is the cognitive process, containing both emotive and conative aspects of human experience, but without the enlarged egoistic emotions and dogmatic graspings characteristic of the next two transformations.”

Representational theories of consciousness like the global workspace theory (Baars, 2013) are generally not concerned with properties of conscious experience like continuity. The ARAS model postulated to handle MPEs is a special representational model and prima facie, it appears that is not concerned with explaining specific phenomenological aspects like continuity of conscious experience (Metzinger, 2019). In addition, while the ARAS signal is continuous, the ARAS model itself is not continuous.

Consciousness Without Content and Theories of Consciousness

A prominent cognitive theory of consciousness is the global workspace theory (Baars, 2013). The global workspace theory, at its core, is a representational or functionalist theory. What one is conscious of is what is globally broadcasted in the brain or mind. If this is the case, and if consciousness is present without content, then this would imply that nothing is broadcast. This seems to go against global workspace workspace theory and representationalist theories, in general (unless the no-content is made into a special non-intentional, non-conceptual content as in the ARAS model). Even if somehow workspace itself is represented and there is no other content, this would still be semantic content (Josipovic, 2019). The maintenance of any content in the global workspace would still need attention and monitoring.

While Baars (Baars, 2013; Josipovic and Baars, 2015) seems to be sympathetic to the possibility of consciousness without content, the implications of consciousness without content for global workspace needs to be explored in detail. It appears that alaya–vijnana or bhavanga awareness cannot be easily accommodated by purely content-based theories of consciousness, since processes operating on content are what makes cognitive or access consciousness possible.

How would other theories of consciousness address the possibility of consciousness without content? For example, consciousness has been conceptualized as a meaning-making process or producing information (Marchetti, 2018). Marchetti (2018) focusing on the content of conscious experience say that “the content of CI coincides with its form.” Given this conceptualization, it is not clear how consciousness without concept can be conceptualized. One could argue for the notion of “pure attention” as a process that does not have content but holds the system in a state of readiness within this theoretical framework (Marchetti, 2018). This is somewhat akin to the proposal of tonic alertness as a possible representational substrate for minimal phenomenal experience (Metzinger, 2020).

Integrated information theory (IIT) is another prominent theory that has been proposed to understand consciousness (Tononi, 2004; Tononi et al., 2016). Tononi et al. (2016) state “Similarly, IIT predicts that the cerebral cortex as a whole may support experience even if it is almost silent, a state which may perhaps be reached through meditative practices designed to achieve ‘naked awareness’ without content (pp. 460).” They also state “States of naked awareness could be compared with states of unawareness that occur, for example, during deep sleep or anesthesia, when the cause-effect repertoires of cortical neurons, regardless of the level of neuronal activity, are disrupted as a result of bistability (pp. 460).”

Dimensional models of consciousness (Berkovich-Ohana and Glicksohn, 2014; Paoletti and Ben-Soussan, 2019, 2020) also try to account for consciousness without content and how they can be achieved. In these dimensional models, time and emotion constitute two dimensions. The third dimension varies: access, varying from low accessibility to high accessibility (Berkovich-Ohana and Glicksohn, 2014) or motivation/self-determination (Paoletti and Ben-Soussan, 2020). The time axis goes from past to future and the emotion axis goes from reward to punishment. They intersect at a point which represent “present” in the time axis and zero emotion in the time axis. Defined in terms of access to awareness (Berkovich-Ohana and Glicksohn, 2014), the third axis goes from minimum access to maximum access or no-access to maximum access. In terms of self-determination (Paoletti and Ben-Soussan, 2019, 2020), the focus is on a particular form of intentionality to act and being aware. The origin or intersection of the all three dimensions possibly represents the state of consciousness without content, which they call the “place of pre-existence” (Paoletti and Ben-Soussan, 2019). It has been argued that such a state of no-self and lack of content is achieved through meditation or possibly sensory deprivation.

How would predictive processing theories handle consciousness without content? Some recent attempts have been made to understand meditation and meditative experience in the context of the predictive processing approach (Lutz et al., 2019; Pagnoni, 2019). Focused attention meditation can be conceived as a way to minimize prediction error through the processes of focusing attention and eliminating distractions with practice (Lutz et al., 2019). If we regard the mind as a hierarchical predictive control system (Jordan, 2003; Kumar and Srinivasan, 2012, 2014), then perhaps one is in a state of effortless perception in which prediction errors at all hierarchical levels are zero. This would include the ability to predict not signals from external environment but interoceptive signals from the body itself, which would need the ability to control the body as well. The ability to control both the body and mind is possible only through interactions with environment, which may partially address the dark room problem (Friston et al., 2012). If consciousness without content is possible, then it is not necessary to have a dark room per se to have absence of content in experience. If it is so, predictive processing theories may need to explain how it is that we have conscious experience, when there is no content (or minimal content) about which predictive inference needs to be made. Of course, it has been argued that the content is a special type of content, which gives rise to the phenomenological experience of no content (Metzinger, 2020). A speculative solution to this would be continuous-time models of perception, which can realize hierarchical predictive inference (Fekete et al., 2018) and may involve prediction of the vehicle (bhavanga or alaya-vijnana) alongside content of consciousness. That is predictive inference not just about the content of experience but also the dynamical structure of experience embedded possibly on a base consciousness.

One of the phenomenal aspects that is very rarely considered in most of these models or theories of consciousness, is Ananda or bliss. As discussed earlier, the Kashmir Shaivists talk of seven different states of bliss associated with Turiya (Lakshmanjoo, 2017). Since emotions or feelings are thought to be intentional mental states, it is not clear why there should be a reported experience of bliss, if there is no content. Consistent with this argument, bliss is not a phenomenal constraint for MPE according to Metzinger (2019). In the spherical models of consciousness (Berkovich-Ohana and Glicksohn, 2014; Paoletti and Ben-Soussan, 2019), the putative point in the three dimensional space representing a state of consciousness without content has zero emotion (neither pleasant nor unpleasant). It is not clear why this point is associated with reports of bliss. Proposers of nondual awareness do include bliss as one of the dimensions of such an awareness (Josipovic, 2019). The term Brahman, the underlying reality according to the Upanishads is generally characterized as sacchidananda (sat – existence or truth, cit – consciousness, and ananda – bliss). It could be important to consider how ananda is linked to consciousness without content or MPEs, in general.

Conclusions

The presence or absence of content-less state of consciousness has important implications for theories of consciousness (Metzinger, 2019). Many current conceptions of consciousness do not consider a content-less state of consciousness as a possibility and would need to be significantly altered if such a state is possible. We need novel paradigms to study and theorize about such states of consciousness without content or minimal phenomenal experience. A thorough understanding of the phenomenal properties of consciousness and its links to functional or neurophysiological aspects would enable us build a comprehensive theory of consciousness (Josipovic and Miskovic, 2020; Metzinger, 2020). The current paper suggests that focusing on the continuity of conscious experience may necessitate proposing consciousness without content a theoretical necessity. Such states of consciousness have been reported for a long time among practitioners in various contemplative traditions and there is a need to take them seriously to eventually understand consciousness. It also seems to be the case that realizing such an experiential state seem to change one’s life in a significant manner. Hence there is also a need to measure the impact of having experienced such a state in day to day life of those practitioners.