Superpositions of conscious states

Consider this thesis:

1. Reality is never in a superposition of two states that differ with respect to what, if anything, observers are conscious of.

This is one of the motivators for collapse interpretations of quantum mechanics. Now, suppose that S is an observable that describes some facet of conscious experience. Then according to (1), reality is always in some eigenstate of S.

Suppose that at the beginning t₀ of some interval I of times, reality is in eigenstate ψ₀. Now, suppose that collapse does not occur during I. By continuity considerations, then, over I reality cannot evolve to a state orthogonal to ψ₀ without passing through a state that is a superposition of ψ₀ and something else. In other words, over a collapse-free interval of time, the conscious experience that is described by S cannot change if (1) is true.

What if collapse happens? That doesn’t seem to help. There are two plausible options. Either collapses are temporally discrete or temporally dense. If they are temporally dense, then by the quantum Zeno effect with probability one we have no change with respect to S. If they are temporally discrete, then suppose that t₁ is the first time after t₀ at which collapse causes the system to enter a state ψ₁ orthogonal to ψ₀. But for collapse to be able to do that, the state would have had to have assigned some weight to ψ₁ prior to the collapse, while yet assigning some weight to ψ₀, and that would violate (1).

(There might also be some messy story where there are some temporally dense and some temporally isolated collapse. I haven’t figured out exactly what to say about that, other than that it is in danger of being ad hoc.)

So, whether collapse happens or not, it seems that (1) implies that there is no change with respect to conscious experience. But clearly the universe changes with respect to conscious experience. So, it seems we need to reject (1). And this rejection seems to force us into some kind of weird many-worlds interpretation on which we have superpositions of incompatible experiences.

There are, however, at least two places where this argument can be attacked.

First, the thesis that conscious experience is described by observables understood (implicitly) as Hermitian operators can be questioned. Instead, one might think that conscious states correspond to subsets of the Hilbert space, subsets that may not even be linear subspaces.

Second, one might say that (1) is false, but nothing weird happens. We get weirdness from the denial of (1) if we think that a superposition of, say, seeing a square and seeing a circle is some weird state that has a seeing-a-square aspect and a seeing-a-circle aspect (this is weird in different ways depending on whether you take a multiverse interpretation). But we need not think that. We need not think that if a quantum state ψ₁ corresponds to an experience E₁ and a state ψ₂ corresponds to an experience E₂, then ψ = a₁ψ₁ + a₂ψ₂ corresponds to some weird mix of E₁ and E₂. Perhaps the correspondence between physical and mental states in this case goes like this:

1. when |a₁| ≫ |a₂|, the state ψ still gives rise to E₁

2. when |a₁| ≪ |a₂|, the state ψ gives rise to E₂

3. when a₁ and a₂ are similar in magnitude, the state ψ gives rise to no conscious experience at all (or gives rise to some other experience, perhaps one related to E₁ and E₂, or perhaps one that is entirely unrelated).

After all, we know very little about which conscious states are correlated with which physical states. So, it could be that there is always a definite conscious state in the universe. I suppose, though, that this approach also ends up denying that we should think of conscious states as corresponding in the most natural way to the eigenvectors of a Hermitian operator.