Assuming awareness belongs only to creatures like us is a kind of cosmic provincialism.
Across the long arc of scientific discovery, humanity has repeatedly learned it is not the center of things — not of the solar system, not of the galaxy, not of the cosmos. Now two philosophers are extending that humbling pattern inward, to the mind itself, arguing that consciousness is not the exclusive property of Earth's particular biochemistry. Writing from the University of California, Riverside and the University of Lisbon, Eric Schwitzgebel and Jeremy Pober contend that awareness, like a song or a cup, may be achievable through radically different materials — and that across a universe of trillions of galaxies, it would be statistically stranger if it weren't.
- The central provocation is deceptively simple: if a cup can hold water whether made of glass or clay, why must consciousness be made only of neurons?
- The sheer scale of the cosmos creates the urgency — with trillions of planets and at least a thousand estimated sophisticated civilizations, identical biochemistry across all of them strains all probability.
- The philosophers are careful not to overreach, deliberately sidestepping a definition of consciousness and instead building from the narrower claim that it is real, recognizable, and potentially substrate-flexible.
- The debate fractures most visibly over artificial intelligence, where Pober urges caution about silicon and Schwitzgebel warns that rejecting it without cause is simply a new form of the old bias.
- Where the argument lands is not a verdict but a reframing: the question is no longer whether machines can mimic human minds, but what kinds of systems — built from what kinds of matter — are capable of waking up at all.
A question that once belonged to science fiction is now being asked in earnest in philosophy departments: does consciousness require flesh and blood? Eric Schwitzgebel of UC Riverside and Jeremy Pober, now at the University of Lisbon, have written a working paper arguing the answer is almost certainly no — that awareness could emerge in life forms built from entirely different materials than our own, including, they suggest, creatures with skin of stone and brains of crystal.
Their argument turns on a concept called substrate flexibility: the observation that certain properties can be realized through different physical materials. A cup holds water in glass or plastic; a song plays on vinyl or digital file. Consciousness, they propose, may work the same way — a phenomenon achievable through multiple kinds of physical machinery, not locked to one biochemical recipe.
The scale of the universe gives the argument its statistical weight. With roughly a trillion galaxies and planets appearing nearly everywhere, the philosophers estimate at least a thousand behaviorally sophisticated civilizations have existed across cosmic history. For every one of them to have arrived at identical biochemistry would be, they argue, extraordinarily improbable. They frame this as a Copernican principle of consciousness — the assumption that awareness belongs only to creatures like us is a form of terrocentrism, a bias as unfounded as believing the Earth sits at the center of the cosmos.
The argument inevitably reaches artificial intelligence, and here the two philosophers part ways. Pober cautions that flexibility across some substrates doesn't mean all substrates qualify, and he is skeptical of silicon. Schwitzgebel takes a broader view: once human biology loses its privileged status, he argues, it becomes difficult to exclude silicon simply for being silicon. Both agree, however, that the real question has never been whether a machine can replicate a human brain — it is what kinds of systems, made of what kinds of matter, have the capacity to be conscious at all.
A question that belongs in science fiction is being asked with complete seriousness in philosophy departments: Does consciousness need to be built from flesh and blood?
Eric Schwitzgebel, a philosophy professor at the University of California, Riverside, and Jeremy Pober, a former graduate student now at the University of Lisbon, have written a working paper arguing that the answer is almost certainly no. They contend that consciousness could emerge in life forms made of entirely different materials than those that built us—imagine, they suggest, a creature with skin of stone and a brain of crystal, something like the alien in the film Project Hail Mary.
The two philosophers are careful about their claims. They don't attempt to define consciousness itself, and they don't assert that such exotic minds definitely exist somewhere in the universe. Instead, they begin with a narrower, more defensible premise: consciousness is real and recognizable. From there, they ask whether it must be tied to the particular biology that happened to evolve on Earth.
Their argument rests on a concept called substrate flexibility—the observation that certain properties can be achieved using different materials. A cup holds water whether it's made of glass or plastic. A song plays whether it's encoded on vinyl or burned to a disc. Consciousness, they propose, works the same way. It's a phenomenon that could be realized in multiple kinds of physical machinery, not locked into one specific biochemical recipe.
Consider the scale of what this means. The observable universe contains roughly a trillion galaxies. Planets appear to be everywhere. The two philosophers conservatively estimate that at least a thousand behaviorally sophisticated civilizations have existed somewhere across cosmic history. If life can take root under wildly different chemical conditions, across that many opportunities, it would be statistically bizarre if every successful lineage arrived at exactly the same biochemistry. The odds simply don't support it.
This connects to a long tradition in astronomy. Each major discovery has nudged humanity further from the center of things—the Earth orbits the sun, not the reverse; our sun is one of billions; our galaxy is one of trillions. Schwitzgebel and Pober extend this humbling pattern to the mind itself, proposing what they call the Copernican principle of consciousness. To assume awareness belongs only to creatures like us, they argue, is a form of terrocentrism—an unjustified belief that life on Earth is uniquely special. It's a bias we should shed.
The argument inevitably turns to artificial intelligence, and here the two philosophers diverge. Pober cautions that flexibility across some substrates doesn't mean every substrate qualifies. Silicon, he suggests, may not make the cut. Schwitzgebel takes a more permissive view. Once you abandon the requirement for human biology, he notes, it becomes harder to defend excluding silicon simply because it's silicon. The material itself isn't the problem—the question is what kinds of systems can actually wake up.
On this they agree: the real question isn't whether a machine can replicate a human brain. It's what kinds of systems, built from what kinds of stuff, have the capacity to be conscious at all.
Notable Quotes
The real question isn't whether a machine can copy a human brain, but what kinds of systems can wake up at all.— Schwitzgebel and Pober
The Hearth Conversation Another angle on the story
When they say consciousness could exist in silicon or crystal, are they claiming it definitely does?
No. They're making a narrower argument—that there's nothing about consciousness that logically requires flesh and blood. The existence question is separate.
But why does substrate flexibility matter? Couldn't consciousness still be unique to Earth biology even if the theory is sound?
It could be, but it would be statistically improbable. If life can arise under wildly different chemical conditions across a trillion galaxies, why would every conscious species use the same recipe?
So this is really about probability, not proof.
Exactly. They're saying: given the scale of the universe and the diversity of chemistry, assuming all consciousness looks like ours is a kind of cosmic provincialism.
Where does AI fit in?
That's where they split. One says silicon might not be the right substrate. The other says once you drop the human-biology requirement, excluding silicon gets philosophically messy.
So we don't know if machines can be conscious.
Right. But we also don't know what would make anything conscious—us included. That's the deeper puzzle they're pointing at.