Hume's internal bundle grows a few extra knots

1 Consciousness is in the brain. Approach pursued by hands-on neuroscientists, such as Susan Greenfield, who seek to understand consciousness by studying the actual material of which our brains are made.It is also the assumption of philosophers ofmind, such as Patricia Churchland and John Searle, although their chief interests are philosophical ratherthan experimental.

2 Consciousness is in the mind. Here wehave the experimental psychologists making a comeback.They have made some spectacular findings, such as Lawrence Weiskrantz's discovery of blindsight. He found that patients witha certain kind of brain damage cannot "see" certain things,but when asked to "guess" what is there, they get it right with inexplicable consistency.This seems to be a case of "awareness" without "consciousness".

3 Computers will explain consciousness. Computers have been one of the main spurs to a renewed interest in consciousness studies. Dan Dennett claims that a computerised robot of sufficient complexity would be both intelligent and conscious. He is even building one to prove it. Roger Penrose disagrees. He accepts that you might be able to build a machine that is conscious, but it would have to be more than a mere computer.

4 The allure of quantum mechanics. One of today's unsolved mysteries is the subatomic world of quantum mechanics. It seems reasonable to look here for a solution to consciousness. So it seems to researchers such as Stuart Hameroff. Others are sceptical, arguing you do not explain a mystery by an enigma.

5 Out of this world. Two groups are seeking the solution to the question of consciousness outside the material realm. One looks to the realm of meditation and mystical experience, the other sees in the mind-over-matter accounts of parapsy-chology a clue to the mind-over matter experience of, say my consciously raising my arm. Susan Blackmore opposes this approach. She can see no connection at all between the paranormal and consciousness.

6 The commonsense approach. The experts deride it as "folk psychology", but the common human experience is of being conscious, feeling in control of our lives and taking responsibility for them.