A WALK in the woods. Every shade of green. A fleck of rain. The sensations
and thoughts bound in every moment of experience feel central to our
existence. But physics, which aims to describe the universe and everything
in it, says nothing about your inner world. Our descriptions of the
wavelengths of light as they reflect off leaves capture something – but not
what it is like to be deep in the woods.
It can seem as if there is an insurmountable gap between our subjective
experience of the world and our attempts to objectively describe it. And yet
our brains are made of matter – so, you might think, the states of mind they
generate must be explicable in terms of states of matter. The question is:
how? And if we can’t explain consciousness in physical terms, how do we find
a place for it in an all-embracing view of the universe?
“There is no question in science more difficult and confusing,” says Lee
Smolin, a theoretical physicist at the Perimeter Institute for Theoretical
Physics in Waterloo, Canada.
It is also one that he and others are addressing with renewed vigour,
convinced that we will never make sense of the universe’s mysteries – things
like how reality emerges from the fog of the quantum world and what the
passage of time truly signifies – unless we reimagine the relationship
between matter and mind.
Their ideas amount to an audacious attempt to describe the universe from the
inside out, rather than the other way around, and they might just force us
to abandon long-cherished assumptions about what everything is ultimately
made of.
Modern physics was founded on the separation of mind and matter. That goes
back to Galileo Galilei, whose big idea, some four centuries ago, was to
boil the world down to the interactions of moving objects that could be
described by mathematical laws. Our senses, meanwhile, lived in the human
soul – distinct, though still important. “Galileo said ‘don’t worry about
consciousness for the moment, just focus on what you can capture in
mathematics’,” says Philip Goff, a philosopher at Durham University, UK.
That philosophical sleight of hand changed everything. The material world
became understandable as Newton and others created “universal laws” that
describe how matter behaves. The achievements since have been stunning:
precise, predictive models of all known elementary particles and forces, and
of the evolution of the cosmos from just after the big bang until today.
These days, precious few scientists would claim to see the mind as
inherently separate from matter. Modern neuroscience has left little room
inside the brain for an immaterial soul. Instead, physicalism reigns – the
idea that everything in nature must be derived from the basic stuff of
physics. It follows that consciousness must somehow emerge out of particles,
strings, information or whatever you take as fundamental.
But while neuroscience can explain with growing precision which kinds of
brain activity map onto conscious states, it is far from understanding why
this brain activity gives rise to conscious experience. This is what the
philosopher David Chalmers called the “hard problem” of consciousness: the
seemingly insoluble question of why matter inside your skull gives rise to a
personal, subjective experience of the world at all.
Some dismiss the hard problem as a red herring. They argue that
consciousness is a useful illusion, or that we will explain consciousness in
physical terms if only we have the patience. But philosophers and
neuroscientists who think the hard problem is real see it as a reason to
call physicalism into question. “The irony is that physicalism has done so
well and explained so much precisely because it was designed to exclude
consciousness,” says Goff.
For physicists, the motivation to rethink matter and mind comes primarily
from another direction – their ongoing attempts to make sense of quantum
mechanics, the laws that govern the behaviour of the atoms and subatomic
particles that make up the deepest layer of reality we know of.
Quantum mechanics was one of two theories that revolutionised physics in the
early 20th century. The other was Albert Einstein’s general relativity. This
says that gravity is the result of mass warping space-time, and it ends up
offering among the best examples of what physicists are striving for – an
objective “view from nowhere” that has nothing to do with the individual
perspective of observers.
Quantum theory was different. Experiments showed that subatomic particles
manifest not in definite states – here or there, say – but as clouds of
probabilities of many different possible states. That fuzziness is captured
by a mathematical entity known as a “wave function”. When we make a
measurement of a quantum object, the wave function is said to collapse such
that the object suddenly has definite properties. The classical world we see
somehow seems to arise out of quantum uncertainty thanks to our
intervention. We as observers bring reality into being.
Or at least that’s one interpretation. Some argue that there is no need to
invoke conscious observers to solve this “measurement problem” and instead
advocate alternative interpretations. Perhaps the most notorious is that,
when the wave function collapses, all possibilities play out in a
near-infinite number of parallel universes. Critics of this many-worlds
interpretation point out that the multiverse is an enormous price to pay to
keep the mind and the observer out of the picture.
Whatever their take on the measurement problem, many physicists agree that a
better understanding of observers would be a boon, and not just for
understanding the quantum world. Quantum mechanics and general relativity
define observers in totally different ways, so thinking deeply about them
could offer clues about how to reconcile the two to give us a unified,
quantum theory of gravity.
The view from nowhere
And then there is time. Here, physics is once again at odds with our
experience, in that general relativity’s view from nowhere holds that
observers, including us, are just coordinates or points in a static chunk of
space-time called the “block universe” – a perfect, unchanging mathematical
object in which past, present and future all exist at once. If that is true,
our experience of flowing time, from the past through the present and to the
future, is merely an illusion.
The problem is that “a view from nowhere is not something anyone’s ever
had”, says Adam Frank at the University of Rochester, New York. We presume
that there is some shared, objective reality out there, but we can never
know for sure. “What quantum mechanics and what questions about time have
both pressed on us is the absolute need to understand the observer, and to
recognise it as a physical constituent of the world,” says Jenann Ismael, a
philosopher at Columbia University in New York. For centuries, we could
ignore observers with little consequence, she says. Not any more.
One option is to suggest that some form of consciousness, however
fragmentary, is an intrinsic property of matter. At a fundamental level,
this micro-consciousness is all that exists. The idea, known as panpsychism,
rips up the physicalist handbook to offer a simple solution to the hard
problem of consciousness, says Goff, by plugging the gap between our inner
experiences and our objective, scientific descriptions of the world. If
everything is to some extent conscious, we no longer have to account for our
experience in terms of non-conscious components.
But most physicists aren’t buying that. Extending the fundamental stuff of
physics to include micro-consciousness would disrupt our remarkably
successful account of how the universe works, says Sean Carroll at the
California Institute of Technology in Pasadena. We have little idea of what
consciousness is, and so adding it directly into such precise and definitive
equations could knock everything else off-kilter. “To start with the
least-well-understood aspects of reality and draw sweeping conclusions about
the best-understood aspects is arguably the tail wagging the dog,” Carroll
wrote in a recent issue of the Journal of Consciousness Studies dedicated to
the mind-matter question.
Goff counters that the only way to make sense of our subjective experiences,
or “qualia” – such as the redness of a sunset or the sharpness of a lemon –
is to treat them as new data that science must include. This new approach
complements rather than contradicts physics, he says.
Where to begin? We should be sceptical of attempts to amalgamate lots of
little bits of micro-consciousness to create complex consciousness, says
Eleanor Knox, a philosopher at King’s College London, because it isn’t how
anything else in physics works. “That’s the old-fashioned Lego brick view of
how we build things up in the universe,” she says. “What panpsychism doesn’t
take at all seriously is the complexity of the story that we already have
about emergence in the world.”
Emergence is the idea that behaviours and properties that don’t seem to
exist when we look at the individual components of a complex system suddenly
take shape when we see the system as a whole. Emergent phenomena are,
essentially, more than the sum of their parts. Individual water molecules
aren’t wet, for instance, and yet wetness is a property of water.
To create a picture of how things work at a higher level, we don’t just
simply combine particles from the bottom up. If we did, we would barely be
able to explain how a kettle boils – never mind why our experience of time
doesn’t stack up with the timeless block universe. Instead, we have to add
in top-down information. The same physical laws act on water molecules in a
liquid and in a gas, but flipping the switch on your kettle changes the
temperature and puts a new condition on the overall system so that the same
laws have a different effect.
Emergence gives physics new explanatory powers, says Knox – but it is far
from understood. “Even thinking that fundamental physics has something to
say about my coffee cup is really complicated, and there are explanatory
gaps”, says Knox. Still, Carroll argues that if we can better understand the
messy complexities of emergence, we might make sense of our role as
observers in quantum reality. We may even find clues as to how Einstein’s
smooth space-time appears out of the grainy picture depicted by quantum
theory. Physicalism could yet survive.
Others advocate a more radical approach. For Smolin and Marina Cortês at the
University of Lisbon, the problems we have are related in a different way.
We can gain a better understanding of quantum reality – but only by
accepting that conscious awareness is tangled up with the nature of time.
Together with independent philosopher Clelia Verde, Cortês and Smolin are
taking tentative steps towards a new theory of quantum gravity that folds in
qualia. It starts with a conviction that the timeless block universe
depicted by general relativity is wrong. Instead, Smolin says that we should
take our experience of time seriously and recognise that things only exist
in the present moment. Nothing persists, things only happen. “For me, time
is absolutely fundamental,” he says. “And there is one property that
mathematical models don’t have, which is that nature seems to be organised
as a series of moments.”
This leads to a very different cosmology, one rooted in present events and
the relationships between them, rather than objects sitting in space-time.
Each event has a view of the world that provides information about how it
fits into the rest of the world – in particular, what its progenitor events
in the past were and how it came to be formed from them. In this “causal
theory of views”, quantum mechanics and space-time aren’t fundamental, but
emerge out of this network of views of events. As events come to be, they
make ambiguous possibilities definite; the unknown future becomes the
present moment. And in this time-created world, physical laws aren’t fixed
like Galileo or Newton supposed, but evolve through time.
Intriguingly, this opens the door to qualia and conscious awareness. That is
because in this picture, there are two types of events. Some events can be
predicted, at least statistically, based on what has happened before. But if
physical laws evolve, then there are other, rarer events whose outcome is
not habitual. These totally novel events, free from precedent, allow the
universe to dictate what happens next.
Near the big bang, novel events would have been very common. Consciousness
would permeate the universe in a picture not unlike panpsychism. But as the
universe ages, unprecedented events become much rarer. One potential
wellspring of novelty today, however, is the highly complex human brain.
Perhaps our brains evolved to make use of these novel events and their
freedom to determine the future, says Cortês. The idea is that our awareness
results from this creative freedom.
Taming qualia
“The universe often surprises itself. Qualia are expressions of the universe
to surprise,” Cortês, Smolin and Verde propose in their contribution to the
special issue of the Journal of Consciousness Studies.
All of which is rather bold. “I’m willing to ask questions,” says Smolin. “I
don’t claim to have an answer.” But evidence may come by looking for
parallels in the structure of views of events, on the one hand, and in the
structure of qualia on the other – bridging the void between mind and matter
opened by Galileo. A first step is to make qualia more hospitable to physics
by describing, for example, how certain experiences are bundled together and
enter our stream of consciousness.
Accepting qualia as scientific data is just what Goff has called for. He
wants physicists to go even further than Smolin and Cortês, though. Rather
than finding a home for consciousness in a physical theory, as in the causal
theory of views, Goff reckons that consciousness comes first, and that it is
networks of simple, conscious entities that ultimately realise the
mathematical structures of physics. The challenge is to demonstrate how.
Yet Ismael sees no need for qualia, or indeed our experience of time, to
take on a central role within physics. We can build up a satisfactory
picture of reality, she argues, simply by examining the relations between
ourselves and how we go about doing physics.
Humans have the ability to develop abstractions that are far from our actual
experience, which helps when devising mathematical descriptions of nature.
The mistake we make is when we try to reverse that process of abstraction –
when we try to start from microscopic particles, like atoms and quarks, and
recover our internal experience. “The closest that we get with an objective
description is brain processes,” she says. “We look at that and say: ‘That
has no connection with anything that’s going on up here.’ But that’s partly
because of this process of abstracting outwards.”
In this way, physical theories will always seem to be at odds with our
internal self and the language of experience. The hard problem of
consciousness isn’t something that physicists need to address, says Ismael.
“Physics can move on without worrying about it.”
Carlo Rovelli, a theoretical physicist at Aix-Marseille University in
France, takes things further still. Much of the confusion arises, he says,
because we forget that all phenomena, whether mind or matter, are related to
one another. This relational view, rooted in Rovelli’s research in quantum
mechanics, demotes the physical objects that are usually the starting point
for fundamental physics. “The best description we have about the world is in
terms of the way systems affect one another,” says Rovelli.
In which case, Galileo’s distinction between subject and object is blurred,
as everything is both a subject and an object – including observers and
their minds. There is no view from the outside. In this way, Rovelli sees
the relational universe as a “very mild form of panpsychism” in that there
is something in common between mind and matter. “It is the realisation that
nature is about things that manifest themselves to one another,” he says.
“This takes away much of the mystery of consciousness.”
If Rovelli is on to something, it would leave us with an uncomfortable
truth. The traditional stuff of physics – namely objects with absolute
properties, to which Galileo devoted his life – can’t exist alone. How does
that feel?
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