Hi Kyle and Duanne,
First I apologize for not being able to spend more time in this interesting discussion. Second, I apologize for making too strong a statement in my haste. I said in my title line "we won't" succeed in making a conscious machine.
I should have said, and what I tried to explain in the post, was that, in my opinion, our current ideas of what constitutes consciousness involves something more than, and outside of, the brain. And, that until we understand what that "outside" component is, we won't be able to duplicate the phenomenon of consciousness.
Your discussions (at least the ones I have read so far) lead me to believe that all three of us agree on that.
Before I read what you wrote, and while I was walking our dog, I was thinking of how to explain my position. I was going to explain essentially the same thing Kyle did by pointing out that 250 years ago, the EM spectrum, atomic decay, and the related phenomena and the related current technology would all have been considered "supernatural". Even though we can't confidently guess at what some new discovery might disclose, I think consciousness depends on something as yet unknown. Consider this analogy.
Suppose you could have presented Isaac Newton with a working cell phone (either by resurrecting him into our time, or by going back to his time and surreptitiously building a complete cellular telephone system before you presented him with the instrument). Then you showed him how to call up someone he knew and let him converse with his friend long enough to convince himself that he really was in communication with his friend over the phone.
Then, you challenged Sir Isaac to examine the cell phone all he wanted in order to come up with an explanation for how it worked and to build a machine that would duplicate its capability. It would have been a daunting challenge even for him and there is a good chance he would guess that there was something supernatural involved, and consequently, that building a duplicate might be impossible. (I don't know if Newton ever said "never".)
My point is that I think that there is not only some requisite unknown physical phenomenon (in the sense that EM radiation is neccessary for cell phone operation) but also that there is probably some real structure outside the brain that is comparable to the extensive set of structures making up the cellular telephone system that are outside the thing I carry in my pocket. I am pretty sure you two would agree on the first part, but I might be alone on that second part. Nevertheless, that is my best guess, but it remains only a guess.