If I am unable to distinguish between visual stimuli A and B then some properties must be remaining the same each time,
Not necessarily. Here’s what could be happening in your brain and which could underlie your power of discrimination: there is some operator which takes two inputs and produces an output “same” or “different”. Since this operator could, in principle, be anything at all, then it is in principle possible for any two arbitrary inputs to be assessed as “the same” by the comparison operator. They don’t have to have anything in common.
That’s in principle. In reality, we don’t expect brains to be so badly designed. We expect that under normal conditions (though not necessarily in highly artificial laboratory setups which test the limits of perception, such as for example “change blindness” experiments) the comparison operators which operate inside the brain output “the same” only when the two inputs are from objects in the real world which are really pretty similar in some important way. And in the case of an apple versus a fake plastic apple, there is something that does remain the same: the pattern of light traveling in the space between the object and your eyes.
But this common pattern of light is surely not a quale. It’s not even in the brain. In fact, the sameness of the two patterns can be demonstrated by taking a digital photo of each scene and then having software compare the two photos. Can you take a photo of a quale?
Qualia are precisely those properties of my subjective experience which enable me to make these judgements.
We have jumped from “some properties must be remaining the same”—which I’ve acknowledged is probably typically the case in normal circumstances—to “properties of my subjective experience”. So we’ve slipped in the term “subjective experience”.
Not necessarily. Here’s what could be happening in your brain and which could underlie your power of discrimination: there is some operator which takes two inputs and produces an output “same” or “different”. Since this operator could, in principle, be anything at all, then it is in principle possible for any two arbitrary inputs to be assessed as “the same” by the comparison operator. They don’t have to have anything in common.
That’s in principle. In reality, we don’t expect brains to be so badly designed. We expect that under normal conditions (though not necessarily in highly artificial laboratory setups which test the limits of perception, such as for example “change blindness” experiments) the comparison operators which operate inside the brain output “the same” only when the two inputs are from objects in the real world which are really pretty similar in some important way. And in the case of an apple versus a fake plastic apple, there is something that does remain the same: the pattern of light traveling in the space between the object and your eyes.
But this common pattern of light is surely not a quale. It’s not even in the brain. In fact, the sameness of the two patterns can be demonstrated by taking a digital photo of each scene and then having software compare the two photos. Can you take a photo of a quale?
We have jumped from “some properties must be remaining the same”—which I’ve acknowledged is probably typically the case in normal circumstances—to “properties of my subjective experience”. So we’ve slipped in the term “subjective experience”.