Can we imply consciousness through functional equivalence?

I was chatting to mark tonight about the consciousness stuff.  I ended with idea that the subjective experiences seem unable to be proven, but what if we could show two minds to be equivalent, by way of modelling their execution or function.

Mark said that we can't even do that for two humans, but we especially can't do that between a human mind, and an artificial mind, because an artificial mind had an intelligent designer, that is, it's function is completely determined, whereas we cannot know if we have fully captured the functioning of the human mind - there might be some aspect that we have missed, and we would never know - perhaps this missed aspect is significant in making the two systems unequivalent.

I said, well what about "for all practical purposes" , I mean, we are able to explain things at a molecular level, like ATP production or photosynthesis, and we could just use occam's razor and assume that the simplest working model is good enough.  I know this still doesn't preclude that perhaps there is a process that we aren't aware of, that is responsible for this subjective experience we are trying to pinpoint.

But the fact that Mark went so far as to say that you can't assume two human minds are equivalent, annoyed me.  He also started making some point about how perhaps I think they are equivalent because the alternative, ie. accusing someone of not being sentient, is undesirable.

I started getting pissed off at him, and didn't want to continue the argument. I felt that he wasn't taking my arguments seriously and at times completely missing the point I was trying to make.

It is not helpful to get emotional when arguing.  I need to practice not getting emotional, and instead dealing with the thoughts and ideas that come up, and see where they lead.

One thing I did find interesting about what Mark said - he said something about  how we seem to only require a theory when there is some deviation that needs to be explained.  Eg. we assume that other people are sentient   as well because there is no reason not to?  something like that