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Is Everything A Computer?

Paul Austin Murphy computes the probabilities.

The term ‘computer’ is both vague and broad. Some people involved in the field of artificial intelligence even believe that molecules are computers. Or, more precisely, they argue that molecules are closed physical systems which compute. That is to say, molecules carry out information processing: they receive input, work on that input, and then produce output. Indeed, in one place I came across the following representation of the DNA molecule as a Turing machine:

Input Tape = DNA
Tape Reading Head = Ribosome
State Register = RNA
States = Amino acids
Instruction Table = DNA codon table
Output Tape = Proteins
(see ‘Is DNA a Turing Machine’ by Anand Mallaya, at anandcv.wordpress.com)

The idea of computation as omnipresent reaches its zenith with what’s called pancomputationalism. This is the view that the entire evolution of the universe is a computation. That must mean, according to some, that God is a computer programmer.

Again and again the issue of what we can or can’t call a computer seems to come back to the vagueness of the word ‘computation’. One way this issue can be approached is to admit that in certain senses the mind-brain system is indeed a computer, in that it carries out computations. However, all sorts of philosophers have argued that computation isn’t definitive of mind: it’s not necessary, or even important, to a mind being a mind that it does computations. Or it may be important, though only in the sense that any human mind can do the same sort of operations that any man-made computer can do; or as the American philosopher Hilary Putnam puts it, “every ordinary open system realizes every abstract finite automaton” (Representation & Reality, 1991).

John Searle agrees with Putnam on this. He wrote the following about the broadness of the term ‘computation’:

“The wall behind my back is right now implementing the WordStar program, because there is some pattern of molecule movements that is isomorphic with the formal structure of WordStar. But if the wall is implementing WordStar, if it is a big enough wall it is implementing any program, including any program implemented in the brain.”
(Philosophy in a New Century: Selected Essays, 2008)

“The window in front of me is a very simple computer. Window open = 1, window closed = 0. That is, if we accept Turing’s definition according to which anything to which you can assign a 0 and a 1 is a computer, then the window is a simple and trivial computer.”
(The Mystery of Consciousness, 1990)

Of course there are certain things that computers do which Searle’s wall or window don’t do. There are also indefinitely many things that the mind-brain does that computers can’t do. However, that doesn’t seem to stop people claiming that the mind-brain is a computer.

When people say “the brain is a computer,” most of them really mean that the mind-brain system sometimes and in some ways behaves like a computer. However, other people believe that the human brain is literally a computer. So let’s put some meat on the idea that ‘brains behave like computers’. It amounts to saying that some processing done by brains to some extent parallels what computers do. Indeed the brain’s own neurons process input in ways similar to the logic gates on a microchip. But the neuron’s processing also has some similarities with what goes in a cell, or even in an inorganic or inanimate system. The crunch question may therefore be: how alike are mind-brains and computers when it comes to processing highly complex tasks?

Where does the idea that the brain is a computer come from? Firstly, there are strong links often made between brains, mathematical models and computers. Workers in artificial intelligence are keen to tell us that physicists have created accurate models of all aspects of physical reality, and that these models are essentially mathematical in nature. Thus it’s only one step on from there to say that they’re also computable. Thus a computer can model and compute the whole of physical reality, including the brain. Some go so far as to say that mathematics is synonymous with computation, and through maths we can model all of reality (or at least each bit separately), including the brain. The argument here is, very roughly, that once we have mathematically described all the workings of the brain, then a computer could model brain processes. This makes the brain a computer, they say. Other people talk about ‘simulating’ physical systems rather than modelling them. One such person (Aaron Roth) concludes, “if the brain is a purely physical object, which is the only option consistent with our understanding of how the universe works, there is no reason it cannot be simulated.”

The logic in either approach is simple:

(i) All physical objects or systems can be mathematically simulated/modelled.

(ii) The brain is a physical object or system.

(iii) Therefore the brain can be mathematically simulated/modelled.

(iv) Therefore the brain is a computer.

The problem is the slide from x being computable to x being a computer. Even if the brain or its workings were computable, that wouldn’t necessarily make it a computer. Searle’s wall (or window) is digitally computable, and some subset of its behaviour is the behaviour of a computer; but that doesn’t make either the wall or window a computer. Sure, we can define ‘computer’ in such a way as to stipulate, for example that If the brain is computable, then it’s a computer; and do the same for Searle’s wall or window. If that wall (window, etc.) is computable, then it’s a computer… At this rate, almost everything physical is a computer. But, on the other hand, a proper computer must be able to systematically process input to create output. So a computer mustn’t only be computable, it must also be a computer!

Paul Austin Murphy is a writer on politics and philosophy. His philosophy blog is at paulaustinmurphypam.blogspot.co.uk.