Try to imagine complete absence of content. No thought. No sensation. No perception. No memory. No sense of time passing or not passing.
What remains?
The question seems to point at nothing — the blank that remains when everything experiential has been removed. But notice: even the imagining of this absence is itself a content. The thought of nothing is still a thought. The concept of contentless awareness is itself a concept appearing in awareness.
You cannot actually imagine contentless awareness. Every attempt to do so produces — necessarily — a new content.
And yet.
Deep dreamless sleep is, from the inside, exactly this. No thought, no perception, no sensation, no memory — and yet you wake from it with the report: I slept deeply and well. Something was there. Something registered the quality of the sleep. Something persisted through the absence of all content and emerged with the capacity to report on what was absent.
The Mandukya Upanishad calls this Prajna — the intelligence of deep sleep. And it identifies it as a preliminary pointer toward Turiya — the awareness that underlies all states, including the state of no content.
The non-dual traditions say: consciousness is not produced by content. Content appears within consciousness. Remove the content and consciousness does not disappear. It remains as what it always was — the space in which content appears, the light by which all content is illuminated, the ground from which all content arises and into which it returns. Not nothing. The opposite of nothing — the fullest possible presence, prior to and independent of anything that appears in it.
The contemplative report from deep states of meditation — Samadhi, Nirbija Samadhi — is not the experience of nothing. It is the experience of everything, prior to the division into particular things. Not blank. Luminous. Not absent. Completely present.
The practical test is available without deep meditation. Sit quietly. Let thoughts arise and pass without following them. Do not try to stop thoughts — simply notice the space between them. The gap between one thought ending and another beginning. In that gap, something is present. It is not the absence of experience. It is experience in its most fundamental form — prior to the content that usually monopolises attention.
That gap is the beginning of the answer. The answer itself cannot be thought. It can only be recognised.