Brain stem death, whilst the body's general physiology is supported, indicates a stage below conscious and unconscious activity/control. This indicates that consciousness is a property of the brain and that it probably lies within the brain. WRT the latter point, I have seen no evidence that removing any other body part's activity has a concomitant loss of consciousness (other than a temporary loss due to fainting and not including any brain supporting physiology [e.g. blood circulation or respiration for O2 provision]). Also, I have seen no scientific evidence that one can walk away from one's consciousness or that consciousness can be active after leaving an unconscious body. Of course anecdotal statements exist for the latter but I have filed them in the bin with the deity, where they belong. I also believe you will find much evidence for the maintenance of consciousness after reduction or deletion of many brain regions, as evidenced by birth defects and trauma. Thus it might be possible, eventually, to name a minimum package of brain regions that generate consciousness, noting that some of these regions might be functionally present or absent in a given individual, but probably some regions are required in all individuals.

The following Scientific American Frontiers article serves to indicate that not all brain regions are necessary for consciousness but are necessary for other functions:

Conventional wisdom holds that we use only ten percent of our brains, but a remarkable young woman named Michelle Mack proves otherwise. Michelle was born with half a brain. Her left hemisphere was almost completely destroyed by a stroke she suffered in her mother's womb. But Michelle's verbal and object-recognition capabilities, normally seated in the missing left brain, are hardly compromised.

In "The Power of Half," meet Michelle and Dr. Jordan Grafman, of the National Institutes of Health outside of Washington D.C. Although their work together has just begun, it's already clear that Michelle's right hemisphere controls tasks handled by the left brain in other people. But this compensation comes with a price; Michelle struggles with visual-spatial tasks, which are normally processed in the right brain. It's as if the two abilities, linguistic and visual-spatial, had to duke it out for space in Michelle's brain- and language won.

See: http://www.pbs.org/saf/1302/segments/1302-5.htm

It is incorrect that consciousness does not have a location. I started a separate thread on this topic. For example, our consciousness is located primarily in our brain and not in someone else's brain, so there is some approximate locality. And yet it does not have a precise physical location (e.g. in these cells or those molecules). Perhaps this is what Rick meant. But this is a complex topic.

More accurately, human consciousness is clearly manifested through biochemical processes for the reason cited above.

Consciousness itself is not biochemical. Human consciousness is a systems phenonemon operating at an abstraction layer above the biochemical systems of the brain.

Consciousness is not biochemical in the sense that biochemical molecules are not consciousness. (or if they are, it is in a different way than we are used to). For example, consciousness is not contained within serotin in a way that would be very meaningful to science.

Consciousness could conceivably be created within a silicon-based computing machine (once we understand its mechanisms well enough). In such an implementation, that consciousness would not involve biochemical processes.

We have no evidence for this, but we have for that based (somehow) around the biochemistry of carbon. For all we know, there might be some special emergent property of C-biochemical reactions that that gives consciousness, and that might not be available from silicon. We are so far from being able to explain this issue, and yet we drop into the realms of science fiction before we get to the end of page one of the book. But think about computers incorporating organic chemicals - now there might be fuel for imagination.

It could be that consciousness is derived from mysterious properties of carbon, or from quantum principles. Are these views testable?

There was a time when physicists believed that electromagnetic waves propagated through the ether. But once the formulas for wave propagation were identified, the explanatory mechanism of the ether became not only unnecessary, but a hindrence.

Many hope that consciousness comes from beyond and is channeled into the brain via an antenna of some sort. If the antenna is not the pineal gland, then maybe it is the probalistic uncertainties of quantum mechanics or special properties of carbon. This way of looking at things keeps consciousness in the driver's seat of agency and out of reach of deterministic processes.

We will still need to explain how information gets into and out of consciousness. And I think we will find that the hypothesis of the consciousness-generating medium becomes an unnecessary element of the equation.

Until someone has developed convincing consciousness in the lab, this question may be undecidable. :-)

It will still be undecidable. Because of the privacy of consciouness, nobody will believe any claim of "consciousness in the lab."

This is making a presumption about what people will believe.

People believe all kinds of things. People believe that:

• there is a God despite lack of evidence
• humans have walked on the moon despite the lack of direct experience and the superficial absurdity of the idea
• "life begins at conception" despite a scientific consensus that this is not a meaningful or testable notion

Most people fully accept the idea of conscious robots as depicted in science fiction movies -- at least while they are watching the movie.

The idea of conscious machines seems to be something people are ready to believe provided that two criteria are met:
1. the machine seems conscious in its behavior.
2. the machine is impressively insightful during a conversation using human language

Consciousness is not outside the realm of science. Claims of consciousness will simply require firsthand experience for validation.

The brain is a complicated thing and is currently infeasible to replicate or mimic through technological means. This does not imply it is impossible to replicate other organism's brain states in ourselves; only that the technology and know-how is not currently available. Optimistically, it's just a matter of time, and is not a question of whether it can be done in theory.

One approach is that you sit down at a terminal and communicate with it by typing until you get to know it.

One could imagine a computer equiped with voice synthesis. Could it be distinguished from a conversation with the physicist Stephen Hawking who uses a voice synthesizer?

A machine that can move around and interact with the world (a robot of some sort) would be more interesting because one can do meaningful things with it and discuss shared experiences. Maybe take it out to a movie.

Like with a new theory of physics, there will be those who are unpersuadable. They will reject anything that is not indistinguishable from human.

Turning the question around, is there anything that would convince you?

What if one of us on this bulliten board was a machine?

....through saturation!

I can't be an artifice because I was made by a man (and a woman)!

An artificial machine that could discuss physics intelligently wouldn't necessarily be conscious. There is one activity that does require experience with consciousness, however, and that is philosophy, specifically, ontology.

Descartes claimed to prove that he existed by saying "I think, therefore I am." He had to be conscious of thinking to believe that claim. Any conscious robot would be likely to understand that argument. Never mind that the claim is strictly incorrect. A statement closer to the truth is "I think, therefore thinking exists."

However, an unconscious robot could still falesly claim to be conscious. This is a really hard problem, and as I mentioned before, probably not solvable. We need to find a test that will prove that artificial consciousness exists.

Suppose we encounter an artificial being who claims to be conscious. What set of questions (key) could there be that, when answered correctly, would prove or disprove it? I think the correct answers are computable, and therefore answerable by unconscious computers.

Here's the proof: complete knowledge of English syntax and semantics is obtainable by artificial devices (computers). Some answers to key questions will be considered to be correct by humans. Humans will be able to communicate with other humans about why those answers are correct. That is, humans will necessarily agree on any any set of questions that can define consciousness, if such a set of questions should exist. Therefore, the correct answers must be computable because they are communicatable.