Dualism and Quantum Physics
We are children of the Enlightenment – empiricists, or ‘Brights’ in Paul Geisert’s designation.) No other-worldly superstitions for us. In our world-view, objective physical reality is the only reality there is. It’s not only ‘out there’ – it’s what you and I are made of. My consciousness is an exquisite illusion that comes about whenever a computational engine is sufficiently large and sophisticated as to reflect on its own processes (Douglas Hofstadter’s ‘Strange Loop’). ‘ The mind is what the brain does.’
This is my world view, and, if you are reading this, I’m guessing it’s yours. Our philosophy is soundly rooted in physics. Trouble is – it’s the classical physics of the 19th century.
Historically, the alternative view has been dualism. Dualism is the idea that consciousness or spirit or mind-stuff has an existence in a separate realm, apart from the physical world. Plato afforded the highest reality to a world of ideals, of which our material world is a mere shadow. In the Gayatri (a compact sort of Lord’s Prayer cum Credo of the Hindu world), there are three universes in parallel: the world of spirit, the world of thought, and the material world. The modern dualist world-view was formalized by René Descartes (1596-1650), the foremost mathematician of his day and in all other respects a ‘bright’ kind of guy. The meaning of ‘Cogito, ergo sum’ is precisely that our knowledge of our own consciousness is direct and primary, while knowledge of the physical world is inferred or constructed from our experience. This is an empiricism of a sort very different from what is fashionable today.
In the late 20th century, the computer revolution granted an exclusive imprimatur to logical positivism, and the idea that we needn’t talk about consciousness to account for the world. Mainstream philosophers extrapolated the exponential advance of artificial intelligence, and leapt forward to the expectation that digital machines would do everything that humans can do (and much more) within a few decades. The Scientific Worldview proclaimed its confidence that physical matter explains all. Daniel Dennett’s book Consciousness Explained may be the most extensive and closely-reasoned statement of this philosophy.
It seems the best minds of the world are with us – the realists, the empiricists, the people who reject superstition and dogma – the enlightened ones are all agreed that the Universe is the physical universe, self-contained, needing nothing so insubstantial as ‘mindstuff’ to explain it. If you ask these people why they don’t believe in minds apart from computational hardware, they will answer ‘Science’, and if you pin them down, they will say, ‘Physics’. There is a near-universal belief among scientifically-minded people that physics provides a complete description of how the world works. They may describe a deterministic schema, or if they’re savvy enough to know that God does play dice with the Universe, then they may modify determinism with quantum randomness.
The irony is that people who make this argument are never physicists. Once you’ve studied quantum mechanics, you just can’t think this way any more.
QM is a set of rules for calculation. The rules have been agreed for 80 years, but it’s not clear what they mean, or what underlying reality they describe, because the rules are so alien to our hard-wired intuitions about objective reality. The interpretation of QM – unlike the rules – has been up in the air from the beginning.
In its most standard formulation – called the Copenhagen Interpretation – QM requires a ‘measurer’ that is apart from the universe. Niels Bohr was being very practical when he proposed this stance, a good positivist, talking about only what we know from experiments. The reality he sought to explain involved large lab machines that take measurements on individual atoms, and his minimalist interpretation of QM was firmly rooted in this paradigm. It claims only to explain the results of such physical measurements, and to relate different measurements, one to the next. It never aspired to be a philosophy or a picture of the universe.
When you think of a huge lab machine taking measurements on a single electron, it’s very clear what a measurement is. But physicists as well as philosophers like to ask hypothetical questions about the limiting cases: What if the measuring apparatus is another electron? What if the huge measuring apparatus is regarded as a huge collection of quantum mechanical particles? What if no human reads the dial on the measuring apparatus? Answers to these questions have been proposed, each satisfactory in part, and each profoundly unsettling in its own way.
So here’s the punch line: The pragmatic, minimalist Copenhagen Interpretation of QM is the one that is still most standard among physicists. The Copenhagen Interpretation divides the world into ‘measurer’ and ‘measured’. In its widest sense, the ‘measured’ is the entire physical universe. The ‘measurer’ is us – our conscious minds, apart from the physical universe. Through the Copenhagen Interpretation, QM presents us with Cartesian dualism in a pure form, fully sanctioned by the most conservative physics we’ve got.
To be sure, there are other views that compete with the Copenhagen interpretation. Hugh Everett while a grad student in 1957 came up with a way to interpret QM reality that doesn’t require consciousness apart from matter. He said that every time an interaction takes place between any two particles there is a set of possible outcomes, and they all occur. No choice is made among the possibilities, but the universe splits constantly into many (many!) possible universes in an ongoing process of fragmentation. The standard measurement probabilities that QM computes are then interpreted as proportional to the number of universes in which each outcome obtains. Avoiding the ‘measurement events’ that put the universe in a new quantum state, the Many Worlds Interpretation says instead: all possibilities are happening. The probability of obtaining a given result for a measurement is just the probability that we find ourselves in a particular subset of universes. The wave function doesn’t change with this measurement – rather, the measurement tells you which universe you are in, and that enables you better to compute which universe you’ll be in for the next measurement.
This idea was discarded as preposterous by most physicists for several decades, on the grounds that all those universes were extra baggage that we shouldn’t need just to understand our one universe. But in recent years, physics and cosmology have been faced with paradoxical results that have forced us to accept new and radical frameworks. The idea of counting universes to find the probability of a given event has come up in other contexts, like the Anthropic Principle of Cosmology, and string theory. None of these points directly to the MWI, but rather they’ve softened physicists to the idea that explaining our universe may require placing it abstractly within an ensemble of universes. In this context, the MWI no longer seems radical.
But who are we in the MWI, and which world do we inhabit? I know I don’t experience fragmentation of my consciousness. Is this because I am only looking back, and my view is always from a particular branch? Is there some sense in which my consciousness subsumes all branches, or perhaps all branches in which I am alive? Maybe the branches in which I die remain forever unknown to me, and I experience and I experience only an ever-narrower subset of branches in which my life continues. This is an odd species of personal immortality.
Another interpretation of QM is the Pilot Wave theory of David Bohm (1952). A major attraction of this view is that it avoids randomness and probabilities completely. ‘God doesn’t play dice.’ Bohm does away with the wave function that is the basis for calculating probabilities in QM, and replaces it with a fully deterministic theory. The catch is that the Pilot Wave is guided not only by local physics but also by influences from all of space and all of time. It’s a radical departure from causality, in the sense that the future influences the past just as directly as the past influences the future. Our normal notion of causality (which is a foundation of the conception of space and time which is Einstein’s greatest legacy) – this conventional causality is half the story and half the influence. The other half comes from everywhere and all time, and that’s why it appears random in the more conventional formulations of QM. Some physicists look at the scientific evidence for telepathy and precognition and they find it compelling, if puzzling. Perhaps Bohm’s physical picture of the world provides a framework in which paranormal phenomena can be understood.
Later in his life Bohm expanded this idea into an integrated scientific and philosophical system that he called the Implicate Order. To fully understand our Universe, we must view two pictures – the local space-time picture which is familiar to us, and the implicate picture, which is like a hologram. Things that are close to each other and strongly influential in each picture are distant and unrelated in the other picture.
To Descartes, the direct perception of thought and emotion were most real. For us, it has become fashionable to imagine that The World, solid and objective and apprehended by all, is most real. But how do we respond when quantum physics tells us that the solidity of an objective world is illusion? We need not rush to embrace dualism, but we can no longer claim the authority of Science for our belief that physical reality is primary and consciousness secondary.
So choose your poison. The idea that the universe is just physical matter is dead. Untenable. Quantum Physics has bequeathed to us a choice of paradoxical and mystical worldviews. We don’t have to accept dualism, but if we don’t, the options may be even stranger. The greatest irony of 20th Century intellectual history may be that empiricism was carried to its logical conclusion, and it led us to the threshold of mysticism.
– Josh Mitteldorf