For me the sticking point here is what lies behind the assumptions of ‘exists’. This is an imagining, a conceiving, a proliferation. This is the part that is completely insubstantial and unreliable and impermanent! It is simply a conceptualisation. You say ‘rock’… but this, in itself, is what the Buddha is pointing at as a symptom of not seeing reality as it is. You ‘see’ ‘rock’… but not really - you are simply attaching to the conceptual proliferation of a rock. You have created ‘rock’. And due to conventions there is agreement with everyone else - yes that is ‘rock’, and so it is made real - and really exists… not really at all.
Nothing that one can take a stand on - ie a View.
There are multiple suttas that describe this, including AN4.24 Kalakaramasutta
(incl also MN1 )
“In this world—with its gods, Māras and Brahmās, this population with its ascetics and brahmins, its gods and humans—whatever is seen, heard, thought, known, attained, sought, and explored by the mind: that I know.
In this world—with its gods, Māras, and Brahmās, this population with its ascetics and brahmins, its gods and humans—whatever is seen, heard, thought, known, attained, sought, and explored by the mind: that I have insight into. That has been known by a Realized One, but a Realized One is not subject to it.
If I were to say that ‘I do not know … the world with its gods’, I would be lying.
If I were to say that ‘I both know and do not know … the world with its gods’, that would be just the same.
If I were to say that ‘I neither know nor do not know … the world with its gods’, that would be my fault.
So a Realized One sees what is to be seen, but does not conceive what is seen, does not conceive what is unseen, does not conceive what is to be seen, and does not conceive a seer. He hears what is to be heard, but does not conceive what is heard, does not conceive what is unheard, does not conceive what is to be heard, and does not conceive a hearer. He thinks what is to be thought, but does not conceive what is thought, does not conceive what is not thought, does not conceive what is to be thought, and does not conceive a thinker. He knows what is to be known, but does not conceive what is known, does not conceive what is unknown, does not conceive what is to be known, and does not conceive a knower.
Since a Realized One is poised in the midst of things seen, heard, thought, and known, he is the poised one. And I say that there is no better or finer poise than this.
Such a one does not take anything seen, heard, or thought to be ultimately true or false. But others get attached, thinking it’s the truth, limited by their preconceptions.
Since they’ve seen this dart to which people are attached and cling, saying, ‘I know, I see, that’s how it is’, the Realized Ones have no attachments.”
I include a translation of the 6th paragraph by Ven K Nanananda just to round it out a bit more and emphasise the point.
“Thus monks, a Tatagatha does not imagine a visible thing as apart from seeing, he does not inmagine an unseen, he does not imagine a thing worth seeing, he does not imagine a seer. He does not imagine an audible thing as apart from hearing, he does not imagine an unheard, he does not imagine a thing worth hearing, he does not imagine a hearer. He does not imagine a thing to be sensed as apart from sensation, he does not imagine an unsensed, he does not imagine a thing worth sensing, he does not imagine one who senses. He does not imagine a cognizable thing as apart from cognition, he does not imagine an uncognized, he does not imagine a thing worth cognizing, he does not imagine one who cognizes.”
It is interesting to compare Bhikkhu Bodhis translation which uses ‘misconceive’ instead of ‘does not conceive/imagine’ - which implies that there is a correct conceiving… this is entirely the important point - there is no proliferation, no papancha no mannati …
I include the above simply as a point to contemplate during practice, not to argue about or to advance a set View, as it points to looking at and examining the constructing and fabricating properties of the Mind.