It’s with us every waking moment, but we barely give it a whiff of thought. Consciousness, it is often said, is the sea we swim in. It has something to do with the awareness of our surroundings, the experience of feelings, thoughts and sensations, and the very essence of being alive. It’s what makes us us.

Yet despite our intimate familiarity with consciousness, it remains one of the universe’s greatest unsolved mysteries.

It’s conceivable that one day we will be able to fully wrap our heads around the biology of the brain — the mechanics of how our eyes, ears and noses give rise to the experience of sight, sound and smell. Or how a perceived threat might release a fight-or-flight hormone. Or what parts of the brain are activated when we feel love, joy or fear. These physiological processes are fascinating in and of themselves.

But how, and to what extent, does the physical give rise to our conscious experience? At what point does the physical convert into the experiential? And how? Is consciousness just a function of the brain — or is it something more?

Theories of consciousness cut to the quick of what it means to be alive. If consciousness can be reduced to the firing of neurons, and humans really are just sophisticated machines, then ideas like free will, the afterlife and the soul don’t compute. If humans — and by extension, the universe — are at the core simply made of matter, then there’s no room for the immaterial. No room for God.

And it matters profoundly which side prevails. Dave Pruett, a mathematician and former NASA researcher, writes that the current consciousness debate “will ultimately redefine our psychic/spiritual place in the cosmos” — a revolution he says is akin to those Copernicus and Darwin ushered in. The study of consciousness might not change our world, but it could very well rock how we see it.

It’s no secret that the brain, with its more than hundred billion neurons, has something to do with the mind. The Greek doctor Hippocrates, who lived over 375 years before Jesus, called the brain “the seat” of the mind. A generation or two later, Plato and Aristotle batted around the “mind-body problem,” and we’ve been wrestling with it ever since.

The first clue that aspects of consciousness depend on particular parts of the brain came about by accident. The whopper of revealing brain injuries happened on a railroad in Vermont in 1848 when Phineas Gage, a construction foreman, accidentally drove a metre-long iron rod through his head, destroying his brain’s left frontal lobe. He survived, but his personality did such a Jekyll-and-Hyde that even when he recovered, his friends said Phineas was no longer the guy they knew.

We’ve come a long way since then. Developments in psychiatry and the emergence of computational technology and neural imaging techniques have vastly expanded our understanding of the brain. Yet, as much as we’ve discovered about how our grey matter works, the question of consciousness is as vexing as ever.

In the mid-1990s, Australian philosopher and cognitive scientist David Chalmers famously divided consciousness into two types of problems: easy and hard. The (relatively) easy problems, Chalmers stated, are those that could be explained using the scientific method. They would include things like how we attend to stimuli, assess an internal state or integrate information.

Chalmers’ “hard” problem? Pinning down our conscious experience. He uses biblical language to express the central riddle: “How does the water of the brain turn into the wine of consciousness?” In other words, we can discern which part of the brain fires at the thought of camping, but that doesn’t explain why feeling a breeze through my tent window makes me feel calm and happy — or conjures a memory of the time my sons declared they would rather play video games than ever go camping again.

Anyone thinking carefully about consciousness today would agree that it’s key to human life, but that’s where consensus abruptly ends.

Arguments about consciousness divide scholars into two competing camps: the materialists and the dualists. Each theory has numerous mind-bending versions: eliminative materialism, reductive materialism, natural dualism, interactionalist dualism, neutral monism, representationalism — so many of them that they read like ingredients on a cereal box.

The materialists argue that the universe is made solely of matter and that everything — including our thoughts, awareness and the experience of being alive — is the result of physical processes. In humans and animals, they assert, brain matter is the mover and shaker of consciousness, and science will eventually be able to pinpoint and explain it all.

Dualists, on the other hand, say that the mind and brain are separate. The brain is physical, but consciousness is immaterial, ultimately outside the domain of the brain. The dualist camp isn’t made up solely of theologians and philosophers. In 2014, more than 200 scientists from a variety of disciplines signed a “manifesto” charging that materialism neglects “the subjective dimension of human experience,” which leads to a “severely distorted and impoverished understanding of ourselves and our place in nature.”

Chalmers argues that mental states can be caused by physical systems but can’t be reduced to them. For example, you can explain the physical processes that are involved in seeing colour, but you can never sufficiently explain what it feels like to see colour to someone who is blind. That’s something you need to experience to know.

Reducing consciousness to physical processes, dualists argue, leaves out the most important aspect of consciousness: what it’s like to feel like who we are. Measuring brain waves can’t determine what is running through a person’s mind.

Enter the raging philosophical debate about zombies. Could zombies exist? We’re not talking zombies ripped from The Walking Dead television series, but “philosophical zombies” that look, walk, talk and behave like us but don’t have subjective experience or the feelings that underlie behaviour. Imagine a smile, for example, that isn’t generated by any real feeling of happiness. The zombie premise is one of the cornerstone arguments that dualistically minded philosophers use to refute the materialist idea that mind and brain are one and the same.

It goes like this: philosophical zombies are conceivable because it’s within the realm of possibility to construct something that looks and behaves like a human. Therefore, brain states could exist without conscious states. Ergo, brain states aren’t the same as conscious states, so the brain and consciousness are two different things.

Mind and matter just seem different. You can divide the brain into smaller bits (atoms and so forth), but you can’t divide the mind. Unlike your brain, your mind can’t be pinned under a microscope.

Philosophical arguments aside, mind and matter just seem different. Mind can’t be a certain temperature or have a specific electrical charge. And you can divide the brain into smaller bits (atoms and so forth), but you can’t divide the mind. Unlike your brain, your mind can’t be pinned under a microscope.

And then there are occasions when the mind seems to do the inexplicable. The 1977 tennis shoe case is classic. The story goes that “Maria,” a migrant worker, had a near-death experience during a cardiac arrest at a Seattle hospital. While she was being resuscitated, she found herself floating outside the hospital building and saw a tennis shoe, which was later retrieved on a window ledge. Not only did she describe the shoe in great detail, but those who were there say she couldn’t possibly have seen it from inside the hospital.

Studies of out-of-body experiences, near-death experiences and extrasensory perception (ESP) are mounting. Gary Schwartz, a neurology and psychiatry professor at the University of Arizona, believes that the research he and his colleagues are conducting on these kinds of topics proves that there is something immaterial about the universe. Schwartz and others cite such things as the placebo effect, yogic control over the body, and physiological effects induced by hypnosis as incontrovertible evidence that mind and matter are fundamentally different.

Schwartz concludes we’re thinking about the brain backwards: the brain isn’t so much a consciousness controller as a receiver. Drawing a parallel between the brain and a television, he argues that materialists are reaching the wrong conclusion about the source of consciousness. Electrical engineers examining a TV use three tests: correlation (monitoring signals inside the unit to see if they match the images on the screen); stimulation (using electrodes to manipulate various components and noting the effect); and ablation (removing various components of the TV and observing the impact). These three tests, Schwartz notes, are essentially the same ones now being used to test the brain. But where the materialist neuroscientist deduces from these tests that the brain self-creates consciousness, the electrical engineer understands that the television simply detects, amplifies, processes and displays information. “You don’t conclude from those three procedures that the television set created the signal,” he has said.

If Schwartz is right and the brain, like the television, is a receiver of signals, where do they come from? Arguing for the immaterial necessitates having to define it. Philosophers like Alfred North Whitehead, the inspiration for process theology, use ideas from quantum physics to argue that consciousness is a universal and primordial feature of all things — humans, animals, even trees and rocks. According to this view, known as panpsychism, anything that has experience, no matter how basic that experience is, has some consciousness in it. In other words, the brain alone is not responsible for experience, and looking at consciousness only through neuronal activity is narcissistic and naive.

In response to the dualists, materialists turn to Occam’s razor, the idea that the simple solution is likely the right one. Applied to this case, the argument goes that since the known universe is entirely made of matter, then it’s most likely that consciousness is material too.

Already, scientists have successfully created aspects of consciousness by stimulating nerve cells in fruit fly brains (remarkably similar to human ones) to give them memories of trauma they haven’t actually experienced. The ability to inject a mental experience by toying with a fly brain is, for some materialists, an indication that science will one day unearth the physical roots of consciousness. After all, the origins of light and heat were once a mystery too.

Even if ESP and near-death experiences are proven legit — and skeptics question the methodology of these studies and the veracity of Maria’s tennis shoe story, and assert that near-death experiences are hallucinations induced by stress chemicals or starving the brain of oxygen — there’s still enough evidence that the brain mediates consciousness for materialists to conclude that cranial goings-on are responsible for it. Poor Phineas Gage would have still acted like the old Phineas after his accident if his mind and brain were truly separate. How can antidepressants make you feel better or a lobotomy turn you into a shell if the mind isn’t physical? Feeling — anything at all — is what happens when your brain system operates.

But then, materialists have the messy task of explaining how the brain works to produce conscious experience. There’s speculation that neurotransmitters have something to do with it, or minute microtubules found inside brain neurons.

Christof Koch is president of the Allen Institute for Brain Science in Seattle and one of the most enthusiastic neuroscientists I’ve ever spoken to. He believes consciousness emerges from the complexity of the brain. While studying the brains of mice, Koch recently discovered that the claustrum, a fairly obscure brain region underneath the cortex, sends and receives fibres throughout the entire cerebral cortex, connecting many regions in both hemispheres of the brain. He thinks the claustrum might be co-ordinating signals across different brain regions, underlying consciousness. Koch speculates that consciousness is less dependent on location than on sophistication. “Just having a bunch of neurons in itself is not enough for conscious experience to occur,” he says. “They have to be wired up in the right way.” Or maybe it’s all a grand illusion.

That’s what Daniel Dennett thinks. In a TED Talk, the American philosopher, writer, atheist and cognitive scientist throws partially transparent images on the screen hovering over a colourful grid of boxes and asks the audience what they see. Despite concentrating on it, I only see the squares in the background dramatically change colour in the replay when Dennett points it out.

Dennett uses this example of “change blindness” to argue that we can be oblivious to massive changes in our conscious experience. Consciousness isn’t continuous; it just appears to be. It’s an illusion or stage magic — the result of a series of multiple, layered computer programs produced by the brain’s hardware, he says. Sensations like pain and hunger are stimuli that the body uses to get the things it needs to survive.

But then, what’s the point of conscious experience at all? Why don’t our bodies just go about their business with the lights off?

Philosopher Joseph Levine, a professor at the University of Massachusetts, Amherst, coined the term “explanatory gap” in the early 1980s to express the lack of explanation for how physical properties give rise to the way things feel when they are experienced. It seems less a gap and more a gaping hole.

When he published his book Purple Haze: The Puzzle of Consciousness in 2001, Levine considered himself a materialist. He doesn’t any longer.

Levine says that, unlike Chalmers, he doesn’t have a tidy argument to summarize his position; it just gradually donned on him that a materialist approach might never bridge the “explanatory gap.” For a time, he held on to the notion that the lack of concrete evidence for materialism didn’t mean the theory had failed — just that it hadn’t been proven to be true. “I now feel that the best explanation for why we can’t explain consciousness in terms of the physical is that it really is something new added to nature.” Levine thinks that when it comes to understanding experience, both dualist and materialist theories of consciousness have hit a brick wall. “We’re in need of a new idea,” he says.

Maybe down the road we’ll dispense with the old divisions. Christopher Fuchs, a physicist at the University of Massachusetts, Boston, says, “One of the lines of thought I’m quite taken with recently is that the world is made of some kind of neutral stuff that is neither matter nor mind, but something entirely different from both. Calling it ‘matter’ is speaking about only one aspect of it, and calling it ‘mind’ is speaking about another aspect. But the two categories don’t exhaust what it is.” Fuchs’s ponderings sound like the theories of Jesuit priest, philosopher and paleontologist Pierre Teilhard de Chardin, who died in 1955: “There is neither spirit nor matter in the world; the ‘stuff of the universe’ is spirit-matter. No other substance but this could produce the human molecule.”

In the end, trying to explain consciousness is akin to the story of the blind men touching the elephant: the men each touch a different part of the animal, and thus reach very different conclusions about what an elephant is. We all know something about what it means to be conscious, but the big picture is still anyone’s best guess. We are our own greatest mystery. As long as the riddle remains unsolved, the materialism-versus-dualism debate will rage. Faith will sit in the crosshairs. And yet, for all the arguing, or maybe because of it, the convergence of neurology, physics, technology, philosophy and theology on the big question of consciousness will make for exciting dialogue over the coming years. It’s a great time to be alive, whatever that means.

This story first appeared in The United Church Observer’s November 2017 issue with the title “Grey matter.”