Consciousness is subjectivity. Subjectivity is not objectivity. Since physics is objective, consciousness is not physics.
Existence: interaction. If something exists, I must be able to learn that it exists. Exists is a verb: things that exist exist in some manner, which we call their properties. To learn that something exists it is necessary to learn in what manner it exists.
Objective: epistemically available to the third person. This has symmetry: if it is available to one third person, it will be available to all third persons, at least in principle.
Subjective: epistemically available to the first person. This is exclusive with being objective, as I'll show.
Let's cleave the sight of a red ball at its joints.
There's a red ball. The ball scatters photons, which enter the eye, which excites the retina, which sends a signal, which is processed by the visual cortex, which results in the red ball qualia.
There is the idea the visual cortex and the red ball qualia have to be identical, but this is epiphenomenalism. As per Turing, the exact implementation of the cortex is not relevant: silicon, myelin, vacuum tubes, gears and levers, it doesn't matter.
1. These all produce the same qualia.
2. These produce slightly different qualia.
3. These produce no qualia at all - I am somehow mistaken.
The motivation for
2) is to maintain the identity, so as to reconcile consciousness with physicalism. However, this results in epiphenomenalism, and thus still refutes physicalism. If the cortex is fully objective, we can remove all supposedly-subjective features from it without loss of predictive validity, as per Ockham, and thus we have proven they don't exist, as in
2) is either not meaningfully different from
3) or you must accept epiphenomenalism, which is magic.
Epiphenomenalism is self-contradictory.
1. By definition, the epiphenomenal agent cannot causally affect the brain, only the reverse. (Newton's generalized third violation).
2. The epiphenomenal mind does not exist, as far as the brain is concerned - it is not epistemically available.
The mind cannot teach the brain about epiphenomenalism.
3. The brain cannot learn epiphenomenalism. It can only refute it. Further, it will only occur to the brain at all due to noise - consider all the ideas you have not bothered to analyze because they're not true. The brain sees no explanandum.
4. A epiphenomenal mind cannot speak to other minds about its existence.
4. In contradiction, epiphenomalism is popular and seen to explain something. "Recently, epiphenomenalism has gained popularity with those struggling to reconcile non-reductive physicalism and mental causation."
(Ed: I'm trying the numbers thing but I'm skeptical that it in fact improves clarity.)
Conclusion: if you have a mind, not just a brain, if you have a thought at any moment, it disproves physicalism. On request I can also show that all forms of dualism reduce to either physicalist monism or full on Cartesian substance dualism.
Let's look at this from another angle.
Thoughts are subjective by identity.
Imagine a beautiful vista, such as a mountain during sunrise.
That you think this image is beautiful is what causes you to think it is beautiful. Identities are tautological; try to imagine a beautiful image that is ugly. Try to imagine a red ball that is a blue cube. This means you cannot be mistaken about thinking the image is beautiful. The Cogito generalizes; not only can you not be mistaken about your existence, you cannot be mistaken about the manner of your existence.
The subjective existence is not only available to the first person, but necessarily known by the first person.
This means you have a subjective existence.
If this existence is merely privileged access to some parts of physical, objective reality, then epiphenomeanlism obtains.
If a thing can be learned about subjectively by one observer and objectively by all other observers, it can also be learned about objectively by the one observer. This means the subjective is unnecessary to fully predict/explain the behaviour of the thing, which means it is causally impotent, which means it is an epiphenomenon. The subject would be unable to tell other observers about its privileged access, only the objective brain, which would have to learn about itself by the usual objective methods, would be able to communicate.
(Let me disprove epiphenomenalism by demonstration: I have subjective thoughts, about which I cannot be mistaken by identity. You're welcome to believe I am lying, if you wish.)
In contradiction, the objective is never necessarily known by the third person; what you think about an objective entity is not identical to that entity. The subjective is fully disjoint with the objective, epistemically speaking. As per my definition of existence, they must also be disjoint in existence.
(Speculation: time evolution allows a subjective event/existence to diamorph into an objective one and vice versa, just as it allows one particle to transform into another. Deep speculation: where the quantum interaction falls on the probability space is determined by a mind, which causes a thought to diamorph into a past physical event. It is a true decision.)
Consciousness, qualia, is the subjective. What 'green' is, rather than what is it caused by or correlated with, is the thought that looks green, that is green because you think it is green.
At present it is impossible to definitively solve the other-minds problem. However, using this framework, it becomes an empirical question. Consciousness is nonelemental, it has internal causation and thus the mind has internal structure, which will affect the statistical distribution of the behaviour of physical objects it is causally linked to. (Speculation: a usefully testable mind could be built out of silicon for something on the order $30 000.)
However, it is possible to solve the self-mind issue, using intentionality. If you have a thought, then cause a portion of physical reality to mimic it, as the thought mimics physics. If you succeed, then...