(This post grew out of an old conversation with Wei Dai.)
Imagine a person sitting in a room, communicating with the outside world through a terminal. Further imagine that the person knows some secret fact (e.g. that the Moon landings were a hoax), but is absolutely committed to never revealing their knowledge of it in any way.
Can you, by observing the input-output behavior of the system, distinguish it from a person who doesn't know the secret, or knows some other secret instead?
Clearly the only reasonable answer is "no, not in general".
Now imagine a person in the same situation, claiming to possess some mental skill that's hard for you to verify (e.g. visualizing four-dimensional objects in their mind's eye). Can you, by observing the input-output behavior, distinguish it from someone who is lying about having the skill, but has a good grasp of four-dimensional math otherwise?
Again, clearly, the only reasonable answer is "not in general".
Now imagine a sealed box that behaves exactly like a human, dutifully saying things like "I'm conscious", "I experience red" and so on. Moreover, you know from trustworthy sources that the box was built by scanning a human brain, and then optimizing the resulting program to use less CPU and memory (preserving the same input-output behavior). Would you be willing to trust that the box is in fact conscious, and has the same internal experiences as the human brain it was created from?
A philosopher believing in computationalism would emphatically say yes. But considering the examples above, I would say I'm not sure! Not at all!
To clarify: at the present you can't obtain a person's beliefs by measurement, just as at the present we have no objective test for consciousness in entities with a physiology significantly different from our own. These things are subjective but not unreal.
And yet I know that I have first person experiences and I know that I am self-aware via direct experience. Other people likewise know these things about themselves via direct experience. And it is possible to discuss these things based on that common understanding. So, there is no reason to stop using the word "consciousness".
Did you mean, "at present subjective"? Because if something is objectively measurable then it is objective. Are these things both subjective and objective? Or will we stop being conscious, when we get a better understanding of the brain.
Are those different experiences or different words for the same thing? What would it feel like to be self-aware without having first person experiences or vice versa?