> I'm sensing redness here and now, so the sensation of redness exists very clearly tied to a particular point in spacetime. In what sense is the qualia of redness not firmly anchored in spacetime? Of course, you could talk about the concept redness, like the concept Pi, but even then, these concepts exist in the mind of a human thinking about them, still tied to a particular location in spacetime.

But qualia are inherently subjective. You can correlate brain activity (which exists at a position in spacetime) to subjective experience, but that experience is not related to spacetime.

Said otherwise: imagine you are in the Matrix at a coffee shop and sense redness, but your brain is actually in a vat somewhere being fed fake sensory input. "Where" is the redness? You would clearly say that it arises in your brain in the coffee shop. Imagine then the vat is moved (so its position in spacetime changes), your brain is rolled back to its previous state, and then fed the same sensory input again. Where is the redness now?

You can't differentiate the two sensations of redness based on the actual position of the brain in spacetime. For all intents and purposes, they are the same. Qualia only depend on the internal brain state at a point in time and on the sensory input. Spacetime is nowhere to be found in that equation.

> The two brains don't receive the same sensory inputs

But let's say they do. Identical brains, identical inputs = identical qualia. What differentiates both consciousnesses?