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Nick Bostrom claims the theory that conscious experience is computational is "widely accepted among cognitive scientists and philosophers of mind" ("Playthings of a higher mind", THES , May 16). This is unlikely.

Certainly, some cognitive scientists believe the mind is a program, so complex software will be conscious, but many others are sceptical.

Philosophers of mind take diverse positions. Some do not even believe in materialism - mind is brain - let alone support the computer theory. Of the materialists, some argue that computation is purely syntactical and cannot support consciousness.

Bostrom argues that "given substrate independence, it is in principle possible to implement a human mind on a sufficiently fast computer". But he conflates substrate independence - the mind is not dependent on neurons - with computational functionalism - consciousness is computer software. The former does not imply the latter. It is not even possible in principle unless computational functionalism were true. The idea of uploading your mind to a computer is fantasy. Human memory, for example, is completely different from computer memory.

To confuse physical reality with computer simulation is tempting, but the realism of computer games means nothing without the game player/s. Does a simulation of Superman fly?

The computer metaphor has been useful in helping to devise possible mechanisms for cognitive processes, such as perception, but philosophers must be wary of using it to support arguments involving consciousness.

Richard Wilson
Bicester