What if absolutely everything is conscious?

Yet panpsychists like Strawson say that doesn’t actually prove Seth’s point. They’re not claiming there’s no emergence in nature. They’re claiming there’s no radical emergence — no cases where a new property pops up that can’t be explained with reference to the properties of its parts. To say that “at some point there was nothing alive” assumes that there’s a sharp break between living and nonliving stuff. But zoom in enough, and the biochemistry that makes up life is really just physics. Cells, after all, are made of atoms.

Seth acknowledges that he can’t disprove panpsychism. He also acknowledges that materialism, in the form of modern neuroscience, hasn’t yet figured out how exactly consciousness could emerge from cells. But give the field more time and he suspects that it could get there, he said: “the hard problem will seem less hard over time, and may dissolve and disappear altogether.”

Since neuroscience labs haven’t cracked the puzzle yet, some scientists are trying a different approach — and new experimental evidence that may support panpsychism is coming to light.

Michael Levin, a professor of biology at Tufts University, is as empirical as empiricists come. He doesn’t believe we should just be armchair philosophizing about consciousness. “Just having feelings about this stuff is ridiculous at this point,” he told me. “You have to do experiments.”

And it’s his experiments that have led him to believe in panpsychism.

One thing Levin has studied is slime mold. The gooey single-celled organism, which looks like dog vomit, can sometimes be found oozing over a forest floor. Even when it grows to be meters across, it’s always just a single cell. It’s got no brain or nervous system. And yet Levin has found that it can reliably make smart decisions.

Place a slime mold at one end of a maze and a yummy treat, like oat flakes, at the other end. You can watch as the slime mold branches off to suss out all the different possible routes to the oat flakes. It’ll then pull away from the less promising paths, choosing instead to squish itself down the shortest path through the maze.

In 2010, researchers from Japan and the UK arranged little heaps of oat flakes in a layout that resembles the population centers of Tokyo. Then they let a slime mold loose. Lo and behold, the single-celled organism cut the most efficient route to each pile of treats, effectively recreating the map of the Tokyo subway system.

You may be thinking that the slime mold is just acting off pre-programmed reflexes, not choosing or learning anything. A French researcher, Audrey Dussutour, proved otherwise. She put slime mold at one end of a bridge and yummy oatmeal at the other. But she lined the bridge with caffeine, which slime mold hates. At first, the slime mold refused to cross the bridge for several hours. Hungry, it finally braved the caffeine so it could get the oatmeal. Over time, the slime mold stopped avoiding the hated substance. Dussutour showed that the organism had learned something: caffeine wasn’t so scary, after all.

The obvious question here is: How is any of this happening without a brain?!

Hold on, because it gets even weirder. Consider Levin’s experiments with planaria, the humble flatworm. It’s got a teeny-tiny brain, but that’s not so important, a fact Levin proved by… decapitating it.

First, Levin trained these worms to get over their fear of light by dribbling a delicious liver snack into an illuminated section of their petri dishes. The worms, which normally prefer to hang out in the dark, learned to venture into the illuminated section of the dishes for these treats. Presumably, this learning took place in the brain. But then Levin cut off the worms’ heads.

Planaria have an amazing ability to regenerate their body parts, so within two weeks, they grew brand-new heads. And when Levin tested their willingness to venture into the middle of their dishes, he found them surprisingly willing. They somehow remembered the liver treats of yore. But how could they remember that if their brains had been cut off?

All these findings suggest that modern science may have made a big mistake in assuming that cognition is all about the brain. Brain cells, known as neurons, are actually not that special. A key feature of these cells — the ability to send and receive electrical signals — is shared with other cells in your body. And it’s this sensing and communicating via electricity that, Levin suspects, makes basic cognition possible.

We’ve known about bioelectricity for centuries, as you might recall from high school biology: send a jolt through a frog and its leg will twitch, right? But Levin is demonstrating that it plays a much bigger role than anyone realized. He suspects that organisms store all kinds of information not just in their cells, but in the patterns of electrical currents passing between the cells. The specific pattern would convey information to other cells.

And what about plants? After all, we know that plant cells use electrical signaling, too. And over the past decade, scientific experiments have shown that they do a whole lot more than seeking out certain outcomes — like sunlight — and avoiding others. They remember and learn from experience, a fact the ecologist Monica Gagliano established with the help of Mimosa pudica, a plant known for defensively folding in its leaves in response to physical stimuli. Gagliano dropped these plants from a height onto a foam base and, as expected, the leaves curled up at the shock. But after being dropped several times, the plants learned that the drops were pretty harmless, so they kept their leaves open during future drops — even a month later.

Plants have many other tricks up their leaves: they keep track of how long it’s been since bees last visited, they send out biochemical distress signals to other plants, and they appear to lose consciousness when sedated with anesthesia.

Levin thinks networks of electrical signals may be making such things possible: storing memories, learning, solving problems creatively — in short, cognition.

“We know that things that don't have brains have cognitive capacities,” Levin said. “Frankly, I don't understand how it took this long for this view to really come back.” Given what evolution tells us about the gradual development of mind, “there's no getting away from the fact that cognition exists widely and long before brains and nerves appear.”

In case you’re wondering why Levin prefers to speak about cognition, not consciousness: The former is about functional abilities we can observe from our third-person perspective. The latter is about what it feels like to be a creature from that creature’s own perspective — so it’s hard, if not impossible, to get at experimentally. Nevertheless, Levin told me, “If I had to put dollars down right now, I do think that consciousness is very ubiquitous and primary, and I think it does go along with cognition.”

Of course, not everyone is ready to bet on panpsychism. For scientists and philosophers who believe consciousness resides in more than just humans and animals but are not convinced it resides in atoms, there’s a kind of in-between position: biopsychism. That’s the view that all living organisms — and only living organisms — are conscious.

Some scientists are busily amassing evidence that could support that view. Aware that anything with “psychism” in its name will probably be branded as woo-woo, they use terms like “minimal intelligence” or “basal cognition.” Their goal is to investigate signs of cognition at the base of the tree of life — in organisms that have very simple nervous systems or lack them altogether because they appeared early in the story of evolution.

Some of these researchers note that attributing consciousness to, say, plants gels nicely with a theory of consciousness that’s becoming increasingly popular in the scientific community: integrated information theory, which says that consciousness is basically equivalent to integrated information. “Integration” happens when different elements in a system communicate with each other, whether that’s neurons communicating in a brain, or something else. The more integrated information there is in a system, the greater the degree of consciousness it’s got. If the cells in a plant are sharing and integrating information through bioelectricity, maybe it’s not that big of a leap to think the plant has some minimal degree of consciousness.

Evan Thompson, a professor of philosophy at the University of British Columbia, argued in his 2007 book Mind in Life that only humans and animals with nervous systems make the cut. But he later changed his mind. After all, he reasoned, any living thing has to make sense of its environment, pursue its goals, and solve problems in order to survive. Whether you’re a tiger or a fern, a slime mold or a bacterium, you need to find a way to get food, reproduce, and adapt when faced with hostile conditions. By its very nature, living seems to be a process of cognition.

“All life is sense-making,” Thompson told me. “The reason I think we can assume that it’s basic to alllife is that it’s actually much harder to make sense of the idea that a system that produces itself metabolically can have directed, oriented behavior without some kind of motivation or drive that involves affect.”

In other words, what does it even mean to say that a living being is pursuing goals but doesn’t want anything?

The downside for biopsychism, though, is that it’s still stuck with the “hard problem” of consciousness, since it reinforces the idea that there’s a sharp break between conscious and nonconscious or between living and nonliving stuff. And so, philosophers like Strawson and scientists like Levin think we need to go further, all the way to panpsychism.

I asked Levin what he thinks is going on inside a plant when it bends toward the light: Is it just acting mechanically, or does it want the light? “All these dichotomies are false dichotomies,” he replied. “What most people say is, ‘Oh, that’s just a mechanical system following the laws of physics.’ Well, what do you think you are?”

Debates about theories of consciousness are kind of like a party game. The central question is: How low can you go? Are you willing to ascribe consciousness to animals? Plants? Cells? Atoms? Subatomic particles?

Even if you believe that all living things have some degree of consciousness, you might have trouble with the idea that an atom or an electron is conscious. It’s hard to understand what that could possibly look like.

Panpsychist thinkers are quick to explain that they’re not suggesting these particles have complex forms of consciousness, like decision-making or meta-cognition (“I want X, and I know that I want X”). They’re envisioning something way more basic. Remember that to have consciousness is just to have a perspective on the world, a feeling of what it’s like to be you.

“For an electron, there’s no meta-cognition, no decision-making,” Leidenhag said. “But when it encounters another electron with another negative charge, it repels.” For any particle, she suggests, “there’s something that it’s like for it to be attracted or repelled.” This attraction or repulsion is a minimal sense of wanting or not wanting.

“Cognition that’s really, really simple looks like physics to us,” Levin told me. For example, we typically assume a key feature of cognition is intentionality or freedom — being able to choose your own path, as opposed to proceeding down a preprogrammed path. Well, physics tells us that even elementary particles have that, in the simplest possible form: quantum indeterminacy (the idea that the physical facts of the universe seem to be indeterminate on the subatomic level).

In fact, if you ask Levin the classic question — How low can you go? Is there anything in the world that’s not somewhere on the spectrum of cognition? — he’ll tell you: “I don’t believe there is a zero in our world.”

He’s happy to acknowledge that the level of indeterminacy in an elementary particle is a “very stupid-low level of freedom,” but it’s not nothing. And that’s all the panpsychist needs in order to explain consciousness as a simple story of scaling. Once upon a time, there was a little particle that was a little bit conscious. It got together with more particles, and they formed a cell that was a little bit more conscious. It got together with more cells, and they formed an animal that was even more conscious…

But wait a second. There’s a problem for the panpsychist here. If the tiniest particles have conscious experiences, how exactly do they combine to produce a more complex thing with its own conscious experience? What's more, how do we explain things like tables or chairs? Panpsychists generally do not argue that those things are conscious subjects — but how do we explain why they aren’t, while the collection of atoms known as a human is?This is known as the “combination problem,” and it’s typically seen as the biggest challenge to panpsychism. Any panpsychist owes you an explanation of why they think the littlest bits are conscious, and humans are conscious, but the table is not.

Our old friend Giordano Bruno anticipated this way back in the 16th century. He argued that even though the tiniest “corpuscles” inside a table are conscious, they do not produce a unified conscious subject when they come together in the form of an inorganic object. “I say, then, that the table is not animated as a table, nor are the clothes as clothes,” he wrote, but “in all things there is spirit, and there is not the least corpuscle that does not contain within itself some portion that may animate it.”

Panpsychists like Leidenhag make the same move today. “I think it follows our intuitions to say that a table isn't conscious because the parts are not interacting together — there's no real unity going on with a table,” she told me. “Whereas with a plant, there really is clear unity.”

In other words, a plant is a goal-directed system with unity of purpose. Its parts are all working together as a team to perform the essential processes that keep the system running. That’s very different from a table, where particles are squished together but are not collaborating.