Materialism holds the high ground these days in debates over that most ultimate of scientific questions: the nature of consciousness. When tackling the problem of mind and brain, many prominent researchers advocate for a universe fully reducible to matter. ‘Of course you are nothing but the activity of your neurons,’ they proclaim. That position seems reasonable and sober in light of neuroscience’s advances, with brilliant images of brains lighting up like Christmas trees while test subjects eat apples, watch movies or dream. And aren’t all the underlying physical laws already known?
From this seemly hard-nosed vantage, the problem of consciousness seems to be just one of wiring, as the American physicist Michio Kaku argued in The Future of the Mind (2014). In the very public version of the debate over consciousness, those who advocate that understanding the mind might require something other than a ‘nothing but matter’ position are often painted as victims of wishful thinking, imprecise reasoning or, worst of all, an adherence to a mystical ‘woo’.
It’s hard not to feel the intuitional weight of today’s metaphysical sobriety. Like Pickett’s Charge up the hill at Gettysburg, who wants to argue with the superior position of those armed with ever more precise fMRIs, EEGs and the other material artefacts of the materialist position? There is, however, a significant weakness hiding in the imposing-looking materialist redoubt. It is as simple as it is undeniable: after more than a century of profound explorations into the subatomic world, our best theory for how matter behaves still tells us very little about what matter is. Materialists appeal to physics to explain the mind, but in modern physics the particles that make up a brain remain, in many ways, as mysterious as consciousness itself.
When I was a young physics student I once asked a professor: ‘What’s an electron?’ His answer stunned me. ‘An electron,’ he said, ‘is that to which we attribute the properties of the electron.’ That vague, circular response was a long way from the dream that drove me into physics, a dream of theories that perfectly described reality. Like almost every student over the past 100 years, I was shocked by quantum mechanics, the physics of the micro-world. In place of a clear vision of little bits of matter that explain all the big things around us, quantum physics gives us a powerful yet seemly paradoxical calculus. With its emphasis on probability waves, essential uncertainties and experimenters disturbing the reality they seek to measure, quantum mechanics made imagining the stuff of the world as classical bits of matter (or miniature billiard balls) all but impossible.
Like most physicists, I learned how to ignore the weirdness of quantum physics. ‘Shut up and calculate!’ (the dictum of the American physicist David Mermin) works fine if you are trying to get 100 per cent on your Advanced Quantum Theory homework or building a laser. But behind quantum mechanics’ unequaled calculational precision lie profound, stubbornly persistent questions about what those quantum rules imply about the nature of reality – including our place in it.
Those questions are well-known in the physics community, but perhaps our habit of shutting up has been a little too successful. A century of agnosticism about the true nature of matter hasn’t found its way deeply enough into other fields, where materialism still appears to be the most sensible way of dealing with the world and, most of all, with the mind. Some neuroscientists think that they’re being precise and grounded by holding tightly to materialist credentials. Molecular biologists, geneticists, and many other types of researchers – as well as the nonscientist public – have been similarly drawn to materialism’s seeming finality. But this conviction is out of step with what we physicists know about the material world – or rather, what we don’t know.
Albert Einstein and Max Planck introduced the idea of the quantum at the beginning of the 20th century, sweeping away the old classical view of reality. We have never managed to come up with a definitive new reality to take its place. The interpretation of quantum physics remains as up for grabs as ever. As a mathematical description of solar cells and digital circuits, quantum mechanics works just fine. But if one wants to apply the materialist position to a concept as subtle and profound as consciousness, something more must clearly be asked for. The closer you look, the more it appears that the materialist (or ‘physicalist’) position is not the safe harbor of metaphysical sobriety that many desire.