@various
"how you define sentience? It's a bit difficult to do that with a bacterium."

This is a tricky one. On the one hand, you could assume that all life forms are sentient, but on the other hand, you could go as far as to believe that you're the only sentient life-form because you're only aware of your own sentience, in which case, everyone else in the universe may exist solely for your own entertainment.

"but we didn't evolve purely by chance. Evolution is somewhat more complex than that."

There's survival of the fittest which eliminates evolutional dead-ends.

"What's really fun, of course, is to point out to them that since the existence of God can neither be proven or disproven, their atheism is a matter of faith just as much as that which sustains the Pope. You can see them start to fizz as they prepare to tell you how wrong you are."

Science and religion may be like apples and oranges, but faith in science is sort of like a religion. Unless you know everything there is to know about each and every branch of science, you just have to have faith that scientists aren't trying to pull a fast one on you. Atheists may really have a religion that's basically faith in science. One thing that they hope for is that the secret of biological immortality will be discovered before they die. There's no set timetable for innovations in biology - they just hope this one Holy Grail will be reached before they die.

"I don't think we're really concious I just think our brains think we are and make us act as if we were."

But how can you trick yourself into believing you think you're not really conscious. I'm pretty sure self-awareness does not come from an algorithm or a pattern in a neural network.

"I'm pretty sure it would be possible to build an AI (or certainly in the future) that to the outside observer looks as if it is fully concious and understanding of what goes on around it. How is that different to us?"

There's a difference to appearing to be conscious and actually being conscious. A computer is just a machine that follows a set of rules. As far as we know, in humans, there are no rules of thinking. If you study computer science, one of the things you learn about is what the theoretical limits of computation are. You can never achieve self-awareness by computation, but you can make a machine act like it's very aware of what's going on - it just needs external stimuli and a complex set of rules.

@chickenlady:
Or maybe we're actually living on the inside of a concave hollow Earth as described in Martin Gardner's book On the Wild Side?
( mistaspakkaman and the inedible shifting caterpillars, Wed 9 Jul 2008, 22:08, Reply)