I concede that my language is sloppy, but then this is a sloppy area and language is going to let us down. At some point between “light hitting a photoreceptor” and “functioning brain experiencing the qualia ‘red’”, we get something we would call observation. That will be true for any explanation that accepts mind-brain identity. There may not be a sharp line between observation and not-observation as we abstract up to the whole brain, and that is not necessarily a defeater for a theory of consciousness.
However, some of the sloppiness is of course my own; I will attempt to tighten that up:
I did not mean to suggest that merely by entering the skull a causal chain becomes conscious. I mean to talk about subjective experience as isomorphic to function, i.e. mind state-transitions correspond to brain state-transitions. Cabining such function inside a brain is neither necessary nor sufficient to that isomorphism, it’s incidental. Allow me to clarify this point.
Consider again the sunflower, and compare it to a rock (a piece of graphite, say). We can see that light hitting the sunflower has an effect different from light hitting the rock. In particular, the light that hits the rock imbues some energy in the form of heat which is diffused uniformly through the rock. Sufficient light will result in a phase change or other reaction. By contrast, in the sunflower, upon being hit with the light a chemical cascade is initiated, in which energy from other sources is consumed and directed such that the sunflower moves. These reactions are different in kind. We can nitpick how exactly we want to define or express this difference, but I will take it at face value for our purposes here. Furthermore, the reaction of a photoreceptor cell in the eye is similar to the reaction of a photoreceptor cells in the sunflower (although the cell in the eye is more specialized, in the difference-in-kind between rock and flower the eye cell is clearly on the side of the flower). This seems like a non-arbitrary distinction between some portions of the causes effects and the totality. Yes, there is a cause and effect relationship between the rock and the light, but it is different-in-kind from that between the flower/retinal cell and the light.
Brains are effectively networks of this latter type of causal connection. The causal relation between the light and the photoreceptor cell is similar to the causal relation between the photoreceptor cell and the neural cells with which it is connected. One conceptual building block I’m using is chains of these causal connections. But these chains aren’t only neurons in series, but also in parallel: each neuron passes a signal to many other neurons, and these subsequent neurons may be interconnecting, including to neurons earlier in the chain.
In brain architecture, we can identify more or less discrete subnetworks composed of such chains, e.g. the occipital lobe. The occibital lobe consists of many millions of these chains, all trained to parse the signals from the photoreceptors into information about the world as represented by the light that strikes the retina.
Consciousness enters the picture each time some part of the network is causally influenced by a different part of the network, such that the former part is trained to recognize patterns within the latter part. When this occurs, the former part is “observing” the latter part, in the same sense that the occipital lobe is “observing” patterns in the retinal photoreceptors. It’s pattern matching, in the same way that AlphaGo pattern-matches on the arrangement on playing pieces on a Go board.
Consciousness is the mental experience of observing mental experience, which is what we would expect a system that is wired to pattern-match to patterns in its own pattern-matching to report. At lower levels, the network pattern-matches on photoreceptor cells firing. At high levels, other parts of the network pattern-match to collections of neurons firing in the photoreceptor-pattern-matching area. This layering continues, with collections of cells reacting to collections of cells reacting to collections of cells etc. This self-observation within the network is isomorphic to the self-observation of conscious experience.
And again, this is all distinct from the rock because the causal chain isn’t merely energy from light diffusing through this causal cascade, but the light starting a causal cascade that uses separate energy, and indeed depends on excluding diffusive energy (most often by residing inside a solid sphere of bone).
From this rough sketch, we need only abstract up to emotional or intellectual reactions, where the layers of self-referential causation permit highly abstracted patterns to be recognized, e.g. (in a super gross simplification) “ideas” made of “words” made of “sounds” made of “eardrum vibrations”.
This does not seem to fit with the observable ways in which purely ‘body’ causes can affect mind. For example, brain damage changes not only the intensity of mind, but the contents and fine-grained functioning. That makes sense if mind is just the working of the brain, but not if mind precedes the brain.