JS: I like the analogy with novels. Like programs, they are multiply realizable, and they are syntactical objects to which we can attach a semantic interpretation. The deep point in both cases is that the syntax is also observer-relative.
MLU: So, if things like novels and computational states are observer-relative, whether or not a given arrangement of matter contains a particular novel or is running a particular algorithm just depends on how the observer chooses to interpret it. Presumably, that means that it is philosophically disastrous to try to associate minds with computation, because it would mean that whether or not a mind existed in some arrangement of matter would also depend on how observers chose to interpret it -- yet you and I know we are conscious, irrespective of what anyone else thinks, or what interpretations anyone else chooses to make. Unlike a novel, or a computational state, consciousness cannot come and go dependent on how people choose to interpret things. The existence of our minds is a physical fact. The existence of computational states isn't. If you mix the two up you are confused. Would that be a reasonable summary of this?
JS: Yes, I think you give a good summary, but I wouldn’t state it quite that way. Observer relativity does not imply total arbitrariness. The fact that this object in my hand is a knife and not a paperweight is observer relative. But not just anything can function as a knife or a paperweight. The point about the observer relativity of computation is that if you tie the notion of computation to the notion of causation, as I suggested in an earlier answer, then multiple realizability will no longer imply universal realizability. But you still have the remaining fact that computation does not name a physical fact of nature like digestion or consciousness.
MLU: Many people still disagree with you and say that you are simply biased in favor of humans or carbon based life. Now that we are at the end of the interview, what is the most important thing that you would like to say to such people?
JS: This criticism rests on a total misunderstanding of my position. My view has never been that only carbon-based systems can be conscious. We ought to hear the question: “Can you produce an artificial brain that causes consciousness out of materials other than biological tissue?” the same way we hear the question: “Can you produce an artificial heart that pumps blood out of materials other than biological tissue?” We know that the answer to the second question is yes. We do not know how the brain does it, so we do not know to what extent the causal mechanisms are dependent on a specific type of biological base. But there is no logical or philosophical obstacle to building an artificial brain that causes consciousness out of some completely different materials.
MLU: We have gone into some rather deep philosophy here, yet these issues should be relevant to anyone who thinks about our place in the world. After all, we each have a mind, so this is about what we are, and how we are here as conscious beings. I am sure you have given our readers something to think about!
Professor Searle, on behalf of Machines Like Us and its readers, I would like to thank you for your time.
JS: Thank you for posing such intelligent questions and being so patient with my answers.
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Books by John Searle
Consciousness and Language
Intentionality: An Essay in the Philosophy of Mind
Mind, a Brief Introduction
Rationality in Action
Rediscovery of the Mind: Representation and Mind
The Mystery of Consciousness
For more thought-provoking essays, visit Paul Almond's website.
Read more exclusive Machines Like Us interviews here.