The noun form can be used when something is the nature of the vastu.
Such as heatness. Occupier. Attribute of fire and attribute of space. But the attribute is the nature, and inseparable in all times. Hence can become a noun form.
Atma is the knower in 3 states of waker , dreamer, sleeper. He is always a conscious being, even while sleeping, I am conscious of sleeping. I am hence, can be called consciousness. Consciousness is my nature, and the word consciousness can also be used for me.
Also to be understood, that I am non material. All material , i am aware of. Hence I am non material.
Thereby I am non material consciousness. Only consciousness is nature of the self, and not material. Material is nature of matter. While non material is nature of consciousness.
This is atma , anatma viveka.
Now while discussing dream state, we talk about material of the dream. The material of the dream, in dream , dream mountain IS. It is purely knowledge. Dream knowledge IS.
Knowledge, any knowledge, has name and form, word and meaning, and that which upholds the word and meaning, is consciousness. There is a thought, in every thought, that which is invariable is the knower of the thought. Or thought consciousness.
Such as elephant, bird, sky, tree, words, duck, consciousness, sofa, chair and so on. Here consciousness is present when we think of bird, sky, tree and all those, when we say consciousness, there is no name and form. Bird consciousness is, we can say that. Bird knowledge Is we say. The material of the knowledge is always consciousness. That which is invariable nature of every thought, is consciousness. In every thought, that it is a conscious thought is the invariable part of thought. Thereby consciousness is the essential nature of thought.
So now we have knower consciousness, and knowledge consciousness.
Self is knower consciousness, non material in nature.
However knowledge consciousness, is material, since thought is matter. But it has the nature of consciousness that is inseparable. So we take the consciousness part to be chidabhasa, or reflected consciousness upon thought which itself needs illumination from consciousness, in order to be revealed.
When we look at the cause for material, it is said to be brahman.
Brahman is said to be satchitananda svarupaH.
Sat refers to timeless existence.
Chit refers to consciousness.
AnantaH refers to limitlessness.
This brahman with maya shakti, it manifests as akasha, vayu, tejAh,apah, prutvi, the material manifestation.
The maya shakti is the matter component, and brahman is satchitAnantaH, since it is timeless and not within space and attributeless existence.
With maya shakti, manifestation happens.
So here when we say brahman, or ishvara, we are talking about, the one whose svarupa is satchitananda svarupa.
Next comes the mahavakya tat tvam asi.
Here the tat pada lakshyartha is shudha chaitanyam, or consciousness.
So here what is being said, is that consciousness by itself is none other than brahman, the ishvara.
The jivatma is equated to ishvara here, as the very cause.
If the jagat is real, then ishvara has undergone change. Jagat is material manifestation, and consciousness is manifest as material without undergoing change.
This is possible only if it is a mithya manifestation.
The materiality is an attribute, a superimposition on the reality which is consciousness.
This is what we can relate to as thought consciousness, the reality of knowledge is consciousness and the thought is manifest name and form.
So this knower consciousness, here knowerness is negated as name and form, and the content of the knower is understood as consciousness, which is brahman.
So consciousness, atma, is limitless in terms of space and time, being its svarupa, changeless nature.
With reference to manifestation, such as space, space itself is consciousness brahman.
Spaceness being a material attribute, the reality is non material consciousness, which remain satchitananda svarupa.
Space when we say, there is name space, and that which occupies space, is nature of space. There is name and function. Function being to occupy space.
Air has airness, and space is the reality of air. From akasha comes vayu. Akasha by itself is brahman. Here the attribute of spaceness is available. Is manifest. It was in unmanifest state and is manifest. However, from the self knower, we know consciousness brahman is attributeless. Thereby we can assimilate space being mithya, and spaceness being an incidental attribute of atma, rather than svarupa of atma. It is incidental to atma, and not natural, not svarupa.
So space is atma, time is atma, air water fire all elements is atma. Then their combinations is atma. Ultimately body mind is also atma, so is all the things around, all other beings, incidental attributes, atma with incidental attributes. Atma remains satchitananda, and what it is seen as , are incidental . Thereby the experienced jagat is incidental manifestation of brahman. Brahman is as though manifest. Due to the incidental attributes, it appears to have manifest, but in reality there is no manifestation or unmanifest state. Due to the incidental changing attributes, there is an appearance of manifestation and resolution.