The ultimate destination of the journey

How our minds relate to the cosmos, how the mental relates to the physical, is just the latest battle in what has been a fierce and long-running philosophical war. Descartes split soul from matter in the seventeenth century, framing the universe as a machine that runs according to physical rules. This model was strengthened by Galileo, who insisted that the book of nature is written in mathematics, and Newton, with his hugely successful physical laws. But not everyone agreed that the universe’s objective and subjective sides can be separated so easily.

Newton’s contemporaries Gottfried Leibniz and Baruch Spinoza, for example, saw the physical and mental worlds as deriving from the same substance; both advocated versions of panpsychism, which sees mind as a fundamental attribute of matter. The eighteenth century saw the rise of different forms of idealism, which goes further, arguing that the physical world in fact derives from the mind. The Enlightenment philosopher Immanuel Kant, reacting against the idea that we can completely understand the physical world through reason, argued that the reality we perceive – even down to the structure of space and time – is inevitably a function of how our minds work, and can’t tell us anything definite about what lies beyond. Irish bishop and philosopher George Berkeley rejected that physical objects can even exist independently of our minds,arguing that ‘to be is to be perceived’.

By the nineteenth and early twentieth centuries, it was seen as a fairly obvious point that physics, which studies objective physical properties, leaves something of nature untouched. The influential philosopher Henri Bergson, for example, emphasised the limits of maths and logic. We hit problems, said Bergson, when we start to believe that the abstract rules and laws of physics are somehow more accurate, more real, than the experiences they were derived from in the first place. We turn life inside out. We conclude that our perception, our existence, is a limited version of the underlying mathematical truth. As Bergson put it: ‘We give a mechanical explanation of a fact and then substitute the explanation for the fact itself.’ When in fact, he argued, it’s the equations and graphs that fail to capture the full, vibrant will and complexity of the actual universe in which we live.

Even philosopher Bertrand Russell – champion of logic and science – pointed out in the 1920s that physics can only reveal the behaviour of matter, not its intrinsic nature (including whether or not this involves consciousness). ‘Physics is mathematical not because we know so much about the physical world, but because we know so little,’ he said. ‘It is only its mathematical properties that we can discover.’ Arthur Eddington, whose 1919 eclipse observations confirmed Einstein’s theory of relativity, built on Russell’s argument in 1928. In fact, he pointed out, there’s one case where we do know matter from the inside: our own brains, which are, of course, aware. Isn’t the simplest assumption that the rest of matter is of a similar nature? It seems ‘rather silly’, he argued, to insist that physical matter must be inherently non-experiential, and then wonder where experience comes from.

At the same time, quantum mechanics was itself casting doubt on what really goes on at the bottom level of existence. As physicists continue to drill down, to study matter at the very smallest scales, objective reality seems to slip through their fingers. Instead of finding particles with definite properties, existing at definite locations, their experiments and hard-won equations yield only probabilities. All possible realities seem to remain in play until they make a measurement, at which point that cloud of possibility abruptly collapses into the single reality that is observed. Hence the famous Copenhagen Interpretation: that it makes no sense to speak about an objective reality other than what we observe. This led to the idea that rather than physicists recording what’s already out there – the dogma since Newton – the very act of looking somehow calls the outcome into being.

From the start, some physicists were horrified by the notion that our conscious minds might determine when and where particles appear. The moon doesn’t exist only when we look at it, Einstein famously insisted. His colleague Max Planck saw the attack on objective reality in science as a ‘moment of crisis’ that threatened civilisation itself. But other quantum pioneers embraced a role for the mind, hoping that their work might help to unify science with mysticism. Einstein’s conviction that reality exists independently of the mind was ‘philosophical prejudice’, said Wolfgang Pauli. Erwin Schrödinger argued that ‘the material universe and consciousness are made out of the same stuff ’, and suggested that science needed ‘a bit of blood transfusion from Eastern thought’.

After the Second World War, this heated debate faded. The role of the conscious observer was never resolved, but through the 1950s physicists came up with other interpretations for their strange results – perhaps particles are guided by a hidden pilot wave, unreachable bymeasurement, or reality splits into multiple parallel universes (an idea known as ‘Many Worlds’) every time an observation is made. These approaches, even if they couldn’t be proven in experiments, allowed the concept of objective reality to be preserved. And quantum theory itself turned out to be exquisitely accurate in terms of predicting the behaviour of the physical world. Scientists dialed down the philosophical arguments and got on with studying that world.

Throughout the second half of the twentieth century, this approach to understanding nature went from strength to strength. Physicists and astronomers armed with general relativity and quantum theory improved their understanding of the universe, building a detailed picture of its history right back to an instant after the Big Bang. Meanwhile biologists gained unprecedented power to explain life’s mysteries. The 1953 discovery of the structure of DNA when combined with the theory of natural selection, was a great leap forwards in understanding howtraits evolve and are inherited.

Even seemingly subjective human attributes – our emotions, perceptions, morals – could be objectively explained as behavioural dispositions, selected for their survival value. And different conscious states were increasingly shown to correlate with physical states and mechanisms in the brain. Our awareness ‘can be bisected with a knife, altered by chemicals, started or stopped by electricity, and extinguished by a sharp blow or by insufficient oxygen’, pointed out Steven Pinker in his 1997 book How the Mind Works. So much, he said, for the supposedly immaterial soul.

Science, it seemed, proved that consciousness is not a fundamental or necessary ingredient in the cosmos. Instead it’s an accidental side effect or by-product of evolution, entirely caused by and dependent on the physical activity of our neurons. The smell of coffee or the prick of a needle; the all-consuming force of a mother’s love; or our transcendent awe at the glittering stars: all of these experiences are decorative. They have no causal role, because everything that happens in the universe can ultimately be reduced to particles and forces, and is decided by physical laws. We might feel like we’re actively thinking up ideas or making choices, but our awareness is simply the output of neurochemical pathways in the brain.

There were grumbling questions. If life is a random accident, why does the universe seem so perfectly fine-tuned for our existence, with physical attributes from the speed of light to the properties of the carbon atom set at just the right level for living, thinking creatures to emerge? Then there’s the simplicity, predictability and even beauty found deep within the equations that describe the structure of the cosmos, where we might have expected messy chaos. In response, physicists appealed to the concept of the ‘multiverse’ – one version of which involves an array of infinite parallel universes, continually bubbling out of each other and all with different physical laws. Just to be able to ask such questions, we’d have to be in a universe that can support advanced forms of life, even if there are countless others that can’t. No purpose or design needed, just blind chance.

Another mystery was why consciousness should have evolved at all, if zombies with the same neuronal activity but no inner experience would function just as well. Or how the rich, qualitative nature of awareness could emerge simply by rearranging dead, dumb atoms. This longstanding question was highlighted in 1994 by philosopher David Chalmers when he called on his peers to address the ‘hard problem’: how can pain, curiosity, the colour red, ever be fully described by the equations of physics? Some responded by simply eliminating the question. A champion of this approach is philosopher Daniel Dennett, who argues that the idea that anything beyond physics exists – what something feels like; a special, extra subjectivity that distinguishes us from zombies – is ‘an illusion’. Beyond the objective properties scientists study – the physical activity of neurons, and the measurable behaviour that results – there is nothing about consciousness to explain.

The claim, ultimately, is that science’s ability to make sense of the world is so powerful, it can explain everything. With it, we transcend the human perspective, the human cosmos, and can see things as they really are. Don’t be misled by our passions and poetry: humans are ‘robot vehicles blindly programmed to preserve the selfish molecules known as genes’ (Richard Dawkins); ‘nothing but a pack of neurons’ (Francis Crick); ‘just a chemical scum on a moderate-sized planet’ (Stephen Hawking). It’s a view that’s not great for our pride, perhaps, but has been undeniably successful in terms of predicting and manipulating the physical world. ‘The reductionist worldview is chilling and impersonal,’ admitted cosmologist Steven Weinberg in his 1992 book Dreams of a Final Theory. ‘It has to be accepted as it is, not because we like it, but because that is the way the world works.’

The latest generation of celebrity physicists has adopted a more conciliatory tone. Maybe we are just accidental passengers in anotherwise barren, pointless universe, but we can still value our brief, unique window of intelligence and self-awareness. Particle physicist Brian Cox suggests we celebrate ourselves as ‘the mechanism by which meaning entered the universe’. In his 2017 book The Big Picture, cosmologist Sean Carroll advocated ‘poetic naturalism’, emphasising that we’re ‘thinking, feeling people’ with many ways of talking about the world. String theorist Brian Greene followed in 2020 with Until the End of Time, devoting several chapters to how religion, literature and art contribute to the ‘nobility of being’. At its root, though, their view of humanity is as hardline as ever.

Carroll insists there is ‘no special mental realm of existence’. Whatever stories we might tell ourselves in daily life, he says, our feelings are simply ‘sets of words’ we use that map onto the physical states of neurons in our brains. There is nothing else. As we make and celebrate our own meaning, we must accept that our inner lives – our sensations, desires, values, feelings, choices, beliefs – have no existence or significance in the physical world.

Greene, too, anticipates that consciousness will turn out to be fully accounted for by conventional physics. ‘The math does rule,’ he writes. ‘We are physical beings made of large collections of particles governed by nature’s laws . . . We feel that we are the ultimate authors of our choices, decisions and actions, but the reductionist story makes clear that we are not. Neither our thoughts nor our behaviours can break free of the grip of physical law.’

For today’s scientific mainstream, this is the final step in our understanding of reality – the ultimate destination of the journey traced in this book. There is no mental realm that physical measurements can’t reach, and even if science hasn’t yet filled in all the details, its approach and methods can ultimately tell us everything we need to know. Sure, we can each find our own meaning in life. But as far as the universe is concerned, ‘you’ (as in your mind, your experience, your self) are either an accidental and transient side effect of blind particle interactions or don’t really exist at all.

This worldview has been pushed hard as the only rational alternative to belief in supernatural gods or souls. But as we fly further into the twenty-first century, the terrain is starting to shift. Respected figures are increasingly arguing that even without God, science is missing something big. In 2012, the atheist philosopher Thomas Nagel complained in his book Mind and Cosmos that the conventional mix of reductive materialism and Darwinism ‘is incapable of providing an adequate account… of our universe’. He was widely criticised for it – Steven Pinker tweeted that the book exposed ‘the shoddy reasoning of a once-great thinker’, while Dennett said it was ‘not worth a damn’ – but Nagel’s not alone. High-profile scientists, too, such as physicist Paul Davies and biologist Stuart Kauffman, reject the idea of a supernatural God but have questioned whether cosmic puzzles such as fine-tuning and consciousness can really be dismissed as random accidents.

Davies, Kauffman and others have suggested that the laws of physics as we know them might not explain everything. Maybe there’s some extra principle, yet to be discovered, that has been nudging the universe towards complexity so that life and consciousness could arise. And a small but growing minority of philosophers is responding in a different way, by reviving an idea that even a few years ago would have been laughed out of town: panpsychism. Maybe, they argue, we have our fundamental understanding of reality upside down. Perhaps consciousness – rather than being an illusion, or a late, accidental, addition to the universe – is everywhere after all.

- Edited extract taken from The Human Cosmos: A Secret History of the Stars by Jo Marchant, published by Canongate Books (£16.99)