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Chalmers and Penrose Clash Over “Conscious Computers”

Philosopher Chalmers thinks computers could be conscious but physicist Penrose says no

Two authors I’ve been reading recently are Roger Penrose and David Chalmers. Penrose is a physics Nobel laureate who has stoked controversy by claiming in The Emperor’s New Mind: Concerning Computers, Minds and The Laws of Physics (1989) that the mind can do things beyond the ability of computers. Chalmers is a philosopher of science who claims in The Conscious Mind: In Search of a Fundamental Theory (1997) that consciousness cannot be reduced to physical processes.

Both thinkers are well respected in their fields, even though they articulate positions that imply that the mind’s operation is beyond current science. At the same time, they believe that there is a way to see the mind as part of nature (that is, naturalistically), albeit from a yet-to-be-discovered point of view. Their approaches to the topic are a rarity when it comes to theories of the mind. The two standard camps are either that the mind is a meat computer or that the mind is beyond the rational analysis of science. In contrast, Penrose and Chalmers believe the mind is both beyond current science, yet not inscrutable to logical and empirical analysis.

Because they arrive at a similar conclusion, we might wonder if their positions are related. They don’t have to be. For example, Chalmers argues that, while the conscious mind cannot be reduced to a physical process, it is possible to imagine a being that is physically identical to one’s self that is also without consciousness (the philosopher’s zombie). Therefore, he thinks, it is possible that a computer program could possess consciousness.

On the other hand, Penrose argues that the non-computable aspect of the mind is generated by a physical process, which he speculates is related to four-dimensional quantum gravity. This is because reconciling two divergent timelines with four-dimensional quantum gravity requires knowledge about arbitrarily distant points, making it an undecidable process, just like the aperiodic tiling concept that Penrose developed. So, on this point, the authors’ conclusions contradict each other.

But Penrose and Chalmers don’t have to contradict each other. What if the human mind is not a computer precisely because it is conscious? This is not so far-fetched. There are a number of concepts of which we are conscious that cannot be computed, for example Chaitin’s unknowable number.

More generally, there is the experience of the infinite and the experience of truth. Let’s see why these concepts are not computable.

The infinite cannot be computed because computers are finite. They can be programmed with rules on how to manipulate symbols of infinity mathematically, but computers cannot figure out these rules on their own. This problem is known as the independence of the axiom of infinity, which means it cannot be derived from any finitist rules of mathematics.

Kurt Gödel (1906–1978) proved that truth is not computable with his Second Incompleteness Theorem. This theorem states that any proof system (including computer programs) that never contradicts itself can never prove this fact. That in turn means that no computer program can have any confidence that any conclusion it draws is true. Therefore, the truth is not computable.

So here we have two things of which we are conscious that are not computable. Of course, we could argue that we are not really conscious of infinity or of the truth. Likewise, we can argue that we are not really conscious at all or that nothing really exists. If, on the other hand, we prefer not to saw off the branch on which we are sitting when we reason, it is clear that it is precisely because we are conscious that our minds are non-algorithmic — which in turn means that intelligence and consciousness are inextricably intertwined.

You may also wish to read: Can quantum physics, neuroscience merge as quantum consciousness? Physicist Marcelo Gleiser looks at the pros and cons of current theories. The problem is, if we assume that “the mind is nothing more than the brain,” there may be nothing we can discover about how it works.


Why physicalism is failing as the accepted approach to science. The argument that everything in nature can be reduced to physics was killed by the philosophical Zombie, as Prudence Louise explains. Physicalism which depends on a mechanistic view of the universe, was challenged by observer-dependent quantum mechanics. Then the Zombie started walking…

Eric Holloway

Senior Fellow, Walter Bradley Center for Natural & Artificial Intelligence
Eric Holloway is a Senior Fellow with the Walter Bradley Center for Natural & Artificial Intelligence, and holds a PhD in Electrical & Computer Engineering from Baylor University. A Captain in the United States Air Force, he served in the US and Afghanistan. He is the co-editor of Naturalism and Its Alternatives in Scientific Methodologies.

Chalmers and Penrose Clash Over “Conscious Computers”