Sunday, May 10, 2020

Consciousness Does Not Compute

nautil |  This past March, when I called Penrose in Oxford, he explained that his interest in consciousness goes back to his discovery of Gödel’s incompleteness theorem while he was a graduate student at Cambridge. Gödel’s theorem, you may recall, shows that certain claims in mathematics are true but cannot be proven. “This, to me, was an absolutely stunning revelation,” he said. “It told me that whatever is going on in our understanding is not computational.”

He was also jolted by a series of lectures on quantum mechanics by the great physicist Paul Dirac. Like many others, Penrose struggled with the weirdness of quantum theory. “As Schrödinger clearly pointed out with his poor cat, which was dead and alive at the same time, he made this point deliberately to show why his own equation can’t be the whole truth. He was more or less saying, ‘That’s nonsense.’ ” To Penrose, the takeaway was that something didn’t add up in quantum theory: “Schrödinger was very upset by this, as were Dirac and Einstein. Some of the major figures in quantum mechanics were probably more upset than I was.”

But what, I asked, does any of this have to do with consciousness? “You see, my argument is very roundabout. I think this is why people don’t tend to follow me. They’ll pick up on it later, or they reject it later, but they don’t follow argument.” Penrose then launched into his critique of why computers, for all their brute calculating power, lack any understanding of what they’re doing. “What I’m saying—and this is my leap of imagination which people boggle at—I’m saying what’s going on in the brain must be taking advantage not just of quantum mechanics, but where it goes wrong,” he said. “It’s where quantum mechanics needs to be superseded.” So we need a new science that doesn’t yet exist? “That’s right. Exactly.”

After we’d talked for 20 minutes, I pointed out that he still hadn’t mentioned biology or the widely held belief that consciousness is an emergent property of the brain. “I know, I know,” he chuckled, and then told me why he felt compelled to write his first book on consciousness, The Emperor’s New Mind, published in 1989. It was after he heard a BBC interview with Marvin Minsky, a founding father of artificial intelligence, who had famously pronounced that the human brain is “just a computer made of meat.” Minsky’s claims compelled Penrose to write The Emperor’s New Mind, arguing that human thinking will never be emulated by a machine. The book had the feel of an extended thought experiment on the non-algorithmic nature of consciousness and why it can only be understood in relation to Gödel’s theorem and quantum physics.

Minsky, who died last year, represents a striking contrast to Penrose’s quest to uncover the roots of consciousness. “I can understand exactly how a computer works, although I’m very fuzzy on how the transistors work,” Minsky told me during an interview years ago. Minsky called consciousness a “suitcase word” that lacks the rigor of a scientific concept. “We have to replace it by ‘reflection’ and ‘decisions’ and about a dozen other things,” he said. “So instead of talking about the mystery of consciousness, let’s talk about the 20 or 30 really important mental processes that are involved. And when you’re all done, somebody says, ‘Well, what about consciousness?’ and you say, ‘Oh, that’s what people wasted their time on in the 20th century.’ ”