Well, since nobody is really answering your question, at least you will be able to get a brief summary of the Advaitin basis of consciousness in these few points of the post:
4. Upadēśa Undiyār verse 23: what exists (uḷḷadu) is what is aware (uṇarvu)
Existence and awareness are inseparable. The very idea of existence arises only because we are aware. If we were not aware, we could not know that anything exists. The only evidence that anything exists is based entirely upon our awareness.
We generally assume that certain things exist even though we are not directly aware of their existence, but the supposed existence of such things is only an idea, belief or inference that arises in our mind and that therefore depends upon our awareness of it as an idea. For example, it is widely believed nowadays that the universe as we know it originated from a ‘big bang’ that occurred about 13.8 billion years ago, but this ‘big bang’ is just a theory or idea that we have read or heard about, and we are told that it is a theory that scientists developed from inferences that they drew from their observations. Even if we understood all the science on which this theory is based, and even if we therefore judged it to be plausible, it would still be for us just an idea that exists only when we are aware of it.
Even the idea that the world existed when we were asleep, or the idea that it existed five minutes ago, are just ideas that exist whenever we are aware of them. We cannot be sure of any such things, and we cannot even be sure that anything that we are currently aware of (except ourself) actually exists, because the seeming existence of such things could be an illusion. All we can say with certainty is that such things and ideas currently seem to exist in our awareness. Therefore the only thing whose actual existence is certain is ourself, the awareness in which other things sometimes seem to exist.
The oneness of existence and awareness (that is, of what exists and what is aware) is explained by Bhagavan in verse 23 of Upadēśa Undiyār :
உள்ள துணர வுணர்வுவே றின்மையி
னுள்ள துணர்வாகு முந்தீபற
வுணர்வேநா மாயுள முந்தீபற.
uḷḷa duṇara vuṇarvuvē ṟiṉmaiyi
ṉuḷḷa duṇarvāhu mundīpaṟa
vuṇarvēnā māyuḷa mundīpaṟa.
பதச்சேதம்: உள்ளது உணர உணர்வு வேறு இன்மையின், உள்ளது உணர்வு ஆகும். உணர்வே நாமாய் உளம்.
Padacchēdam (word-separation): uḷḷadu uṇara uṇarvu vēṟu iṉmaiyiṉ, uḷḷadu uṇarvu āhum. uṇarvē nām-āy uḷam.
அன்வயம்: உள்ளது உணர வேறு உணர்வு இன்மையின், உள்ளது உணர்வு ஆகும். உணர்வே நாமாய் உளம்.
Anvayam (words rearranged in natural prose order): uḷḷadu uṇara vēṟu uṇarvu iṉmaiyiṉ, uḷḷadu uṇarvu āhum. uṇarvē nām-āy uḷam.
English translation: Because of the non-existence of [any] uṇarvu [awareness] other [than uḷḷadu] to know uḷḷadu [what exists], uḷḷadu is uṇarvu. Uṇarvu alone exists as we.
உள்ளது (uḷḷadu ) means ‘what is’ or ‘what exists’, and உணர்வு (uṇarvu ) means awareness or consciousness, but in this context it means awareness in the sense of what is aware. If anyone were to argue that what is aware (uṇarvu ) is something other than what is (uḷḷadu ), that would imply that what is aware does not exist, which would be absurd. Since what is aware must exist in order to be aware, it must be what actually exists. This is why Bhagavan argues: ‘Because of the non-existence of [any] awareness other [than what is] to know what is, what is is awareness’.
If what is (uḷḷadu ) were not aware, it could not be known or experienced, because it would require some awareness other than itself to experience it, and anything that is other than what is (uḷḷadu ) would necessarily be what is not (illadu ), so obviously no awareness other than what is could exist. Therefore only what is (uḷḷadu ) can be aware of what is, so what is (uḷḷadu ) must be what is aware (uṇarvu ). Likewise, what is aware (uṇarvu ) must be what is (uḷḷadu ), because in order to be aware it must exist.
What is aware (uṇarvu ) must actually exist, but other than itself whatever it is aware of need not necessarily exist, because it could be an illusion — something that seems to exist but does not actually exist. Therefore the only thing whose existence is certain is what is aware, and what is aware is ourself, ‘I’. We may not be whatever we now seem to be, but we do exist at least as the fundamental thing that is aware (uṇarvu ).
In the final sentence of this verse he concludes, ‘உணர்வே நாமாய் உளம்’ (uṇarvē nām-āy uḷam ), which means, ‘What is aware (uṇarvu ) alone exists as we’, and which in this context implies also that what is (uḷḷadu ) alone exists as we. In this sentence the absolute identity or oneness of awareness and ourself is emphasised in two ways. Firstly the suffix ஏ (ē ) that is appended to உணர்வு (uṇarvu ) is an intensifier that conveys the sense of ‘only’ or ‘certainly’, so it implies not only that we are what is aware but that we are only what is aware — in other words, we are nothing but what is aware. Secondly, though the subject of this sentence is உணர்வே (uṇarvē ), which means ‘awareness alone’ or ‘only awareness’, and though we would therefore normally expect it to be treated grammatically as a third person, Bhagavan treats it as the first person, because the verb உளம் (uḷam ), which is a poetic abbreviation of உள்ளம் (uḷḷam ) and which means ‘exist’ or ‘are’, is a first person plural form of உள் (uḷ ), which mean to be or to exist.
However, though உளம் (uḷam ) is a first person plural verb, Bhagavan did not intend it to imply that awareness (uṇarvu ) is plural but only that it is the first person, ‘I’. The reason he uses this first person plural form of the verb is that in this context (as he often did) he is using the first person plural pronoun நாம் (nām ), which means ‘we’ in an inclusive sense, as a generic pronoun referring to ourself, so it actually represents the first person singular pronoun ‘I’. Therefore though உள்ளம் (uḷḷam ) or உளம் (uḷam ) is grammatically a plural form, in this context it actually represents the first person singular form உள்ளேன் (uḷḷēṉ ), which means ‘am’, so we can paraphrase the meaning of this final sentence thus: ‘What is aware (uṇarvu ) alone am as I’. In other words, what is aware is only ‘I’, ourself.
Since we are only what is aware, and since what is aware is what is, what this verse implies is that we are both what is aware (uṇarvu ) and what actually exists (uḷḷadu ), and that we are nothing else — that is, we are nothing other than the one reality, which is what exists and what is aware. Therefore since we exist and are aware of our own existence, we are certainly not śūnya in the sense of non-existent or nothing.
5. Emptiness requires the existence of something that is empty
Let us now consider the primary set of meanings of this word śūnya , namely empty or void. The first point to note about the idea of emptiness or voidness is that nothing cannot be empty, since it does not exist, so emptiness implies the existence of something that is empty. Therefore when the terms ‘empty’ or ‘void’ are used in a metaphysical sense, they do not imply an absolute nihilism, as the term ‘nothing’ or ‘non-existent’ would do.
Another point to note about the idea of emptiness is that it is a relative concept, because there can be no such thing as absolute emptiness, since even if nothing else were present in whatever is said to be empty, at least space would be present there. In a physical context, the closest thing to an empty void would be a dark vacuum that contains no subatomic particles, radiation, magnetic field, gravity or any such thing, but even such a void would be filled with physical space.
In a metaphysical context, if something is said to be empty or void, we would have to ask empty or void of what? Even if it were empty or void of all particular things, properties or features, it would still be full of itself, so in that sense it would not be an absolute void or emptiness. In fact, by trying to conceive of the existence of something that was empty of everything except itself, we are led to see that emptiness and fullness amount to the same thing, because what is empty of everything else must be full of itself, and what is full of itself must be empty of everything else.
As a metaphysical concept, therefore, the idea of śūnya or śūnyatā turns out to be a rather empty and unhelpful concept. In the sense of nothingness or non-existence, śūnyatā does not mean anything, because nothingness is not a thing, but is merely a conceptual negation or denial of what is, so outside the world of concepts (the mind) nothingness does not exist and is therefore not anything at all. In the sense of emptiness or voidness, on the other hand, śūnyatā is a vague, uninformative and incomplete concept, because it does not inform us what is empty or of what it is empty.
Hence it is a wonder that the terms śūnya and śūnyatā acquired a place of such central importance in many forms of Buddhist philosophy. Of course these terms can acquire meaning if they are used in the sense of emptiness and with an understanding of what is empty and of what it is empty, but if considered in isolation from such an understanding, they do not unambiguously mean anything at all.
6. Suñña Lōka Suttaṁ: the world is ‘empty of oneself or of anything belonging to oneself’
The Pali form of the Sanskrit word śūnya is suñña , and the earliest mention of this concept in Buddhist texts is found in the Tipiṭaka (the Pali Canon). In the Suñña Lōka Suttaṁ ,for example, it is recorded that when Buddha was asked in what respect the world is said to be empty (suñña ), he replied that it is said to be empty because it is ‘suññaṁ attēna vā attaniyēna vā ’, which literally means ‘empty by ātman or by anything belonging to ātman ’ and which implies ‘empty of oneself or of anything belonging to oneself’, and then he went on to list various things in the world that are ‘empty of oneself or of anything belonging to oneself’, such as each of the five senses, the sensations and objects perceived by each of them, the body, the mind and whatever is known by it. Thus what he said amounted to saying that all phenomena — everything that we experience other than ourself — are ‘empty of oneself or of anything belonging to oneself’, or in other words that no phenomenon is ourself. If understood in this sense, the meaning of suñña or śūnya is quite clear, straightforward and uncontroversial: what is empty is the world or anything other than ourself, and what it is empty of is ourself.
