Does the individual consciousness depend on the actual atoms or only on the configuration of the atoms? Suppose we have mastered cryo-freezing and atom-manipulation technology. We can freeze and unfreeze people at will. We freeze Sarah. We replace Sarah's atoms one by one. With all atoms replaced, we wake her up. Is it the "same" Sarah? (the same to herself, not just to us). Thanks, Mario

If one thinks of 'atoms' as ultimate constituents of matter, indistinguishable apart from their spatial and temporal position, then it is hard to see how changing them for identical duplicates at the same location could make a difference. (I'm interpreting the experiment as replacing every atom with an identical duplicate: same atomic weight, same charge, etc.) After the experiment, one would have replaced every atom with a partner with exactly same causal powers at the same location, and it is hard to see how this could effect an overall difference in her consciousness. The only difference between Sarah before and after the operation is an historical one: the atoms in Sarah after the operation would have a different history to those in Sarah before the operation. But it is difficult to see how this difference could make a difference to Sarah's consciousness. (Going through a freezing process might make a difference to her consciousness though!)

I studied languages, not philosophy, the reason being that I was afraid I would have to study intensely old philosophers and this would influence my own thinking. This was very wise, I think, and now, thirty years on, I think I have developed my own view. Now I would like to see if there are others who think along the same lines. What I try to do is view myself and the rest of us the way humans look at other animals and see the similarities. I consider evolution to be the only driving force in life and therefore our self-consciousness and intelligence to be evolutionary assets like the claws of the tiger or the trunk of an elephant. Could you direct me to others who think along the same lines? Yours truly, Martin C.

Hi Martin. I'm not sure about your justification for not studying philosophy (the intention of which is to encourage thinking things through for yourself!), but you'll be glad to know that there are plenty of philosophers who think along similar lines to those that you mention. There are too many to list, but two prominent philosophers concerned about the kind of big picture that you mention are Daniel Dennett ( Consciousness Explained , Darwin's Dangerous Idea ) and Fred Dretske ( Naturalising the Mind ).