When I open my eye, light hits it, striking off the object which I am seeing. What it means to see is for that object to cause my perception. I am NOT seeing my perception, that doesn't make any sense -- it's incoherent because it's an infinite regress.
When I open my eyes and see the coffee, my body changes to have the perception of that coffee as part of my structure -- I am the photographic plate. Just as the photographic plate isnt taking a picture of itself, neither is my eye or mind.
To see is, akin to the photographic plate, to be changed by the world so that you have an impression of it. You do not see seeing, you see objects.
And the point is that you don't need the "world" aka reality to make that change. It can come from within, for example a faulty sensor creating an image of a cloud that does not exist.
And the implication that follows is that just because you percieve something does not mean that it is "real".
This can be made more clear if you understand that every "real" object is made up of pixe dust aka fields. When you see a particle at some point, say an electron, there is actually nothing there...but the space at that location behaves, for some reason, as if there is an electron there...
And that is another problem with the physical idea. What happens if you continuously split an object? If it is really physical, then it should remain physical no matter how many times it is split. But we see that it is not the case.
The mind doesnt have the right kind of properties to explain that. If you modify "consiousness" to include those properties then it's no longer consiousness at all.
Whatever generates law-like fixed perceptions of the objective has to be as if all of material reality exists in its law-like way.
Yes, P(Material Reality Does Not Exist) > 0 BUT whatever confidence you give to that, say p_illusion,
P(Material Reality Exists as it seems to | the fixed background of law-like perceptions) >>>>> p_illusion
You dont escape the need for the objective, the law-like, the fixed, the external.. just because you locate what generates this in "the mind" (redefined to include this). At that point the "mental origin" of this background is material. You arent making any difference to call it mental or physical.
It discovers no such thing. It can only measure the signals coming from the sensors. That is its ground truth. If a sensor can produce a signal without having an image fall on it, then that would be what the camera sees.
So in this case, it would perceive the image of a camera in a mirror, but that would not be the reality.