This is precisely what Ramana Maharshi taught. Consciousness or pure awareness, the natural state, is only aware of itself. Everything else – all of phenomena, experienced as either inside oneself or as outside oneself – only seems to exist. It is ego…which has nothing to do with our contemporary views of the term. It is also what Sunyo refers to above when he writes:
In Vedanta, it is known as cidabhasa. Without going into detail, it is like moonlight or the shining of the moon. The moon seems to shine or give off light. In reality, it is only reflected light – chidabhasa – that comes from the sun, its source or origin. Likewise, ego (not your or my ego) is like a snake that one – ego – takes to be a rope. Hence, ego, defined as the five sheaths (body, prana or the vital elements, mind, intellect and will) is what seems to exist. Yet we remain in perpetual delusion and ignorance because we take what has (falsely) superimposed itself on reality to be true.
English translation: If the ego comes into existence, everything comes into existence; if the ego does not exist, everything does not exist. [Hence] the ego itself is everything. Therefore, know that investigating what this [ego] is alone is giving up everything.
Which ego is he referring to here? The one and only ego there is, namely ourself, so we are that.
However this one ego is not what we actually are, but only what we seem to be, so if we investigate ourself keenly enough, we will see what we actually are and hence this one ego will vanish forever, since it does not actually exist, just as an illusory snake would vanish if we were to look at it carefully enough to see that it is actually just a rope. Therefore, since the seeming existence of everything else depends upon the seeming existence of ourself as this ego, and since this ego will cease to exist if we investigate it keenly enough, Bhagavan says, ‘ஆதலால், யாது இது என்று நாடலே ஓவுதல் யாவும்’ (ādalāl, yādu idu eṉḏṟu nādalē yāvum ōvudal ), which means, ‘Therefore, investigating what this [ego] is alone is giving up everything’.
So to get back to what you were saying, HinMarkPeng, pure awareness is self shining. Meaning, it is only aware of itself. Everything else only appears or seems to be other (because it is a mix of adjunct conflated awareness – ego – that the latter falsely projects as the real thing). Make no mistake, Maharshi’s teachings are very distinct from the usual repetiton nowadays of both the Classic Vedanta and Neo-Vedanta catch all phrase: “Consciousness is all there is.” Maharshi is saying the opposite. All that we see and experince is ego. It would be too long to explain but to sum it up in simple metaphor: the snake is nothing but the rope, but the rope is not a snake.
No worries, I know 99% of readers here will be hardly interested in this. Yet you would be surprised how Ramana Maharshi spelled out – in deeper and subtler detail than the Upanishads as well as the confusion of millenia of Vedantic commentaries – much of what you are discussing here in a few simple texts, notably Ulladu Narpadu.