University of California, Riverside’s Professor Eric Schwitzgebel and University of Lisbon postdoctoral researcher Jeremy Pober argue that consciousness is substrate flexible, meaning it can arise not just in the biological tissue we find on Earth, but potentially in radically different physical materials found elsewhere in the cosmos.
Jeremy Pober & Eric Schwitzgebel argue that conscious experiences can arise in a variety of different types of physical media, not just in biological animals as they currently exist on Earth. Image credit: Fernando Ribas.
“Who is conscious? We — both authors and you, the reader — are,” Professor Schwitzgebel and Dr. Pober wrote in their paper.
“Some non-human animals presumably are. Likely, as we will argue, some extraterrestrial entities (aliens) are.”
“We don’t think there’s good evidence that current technology has produced conscious artifacts, though we don’t rule out that possibility in the future.”
“What we will argue for is that consciousness can be realized in very different kinds of physical arrangement — different substrates. Consciousness is substrate flexible.”
The observable part of the Universe contains about one trillion galaxies. Planets are common, and the great majority have environments quite different than Earth’s.
For the purposes of their argument, the authors estimate that at least a thousand behaviorally sophisticated species — ones capable of complex communication, goal-seeking, and cooperation — have existed or will exist somewhere in the observable Universe.
Drawing on astrobiology, they also argue that life on other worlds very likely evolved using different chemical building blocks than the amino acids and nucleic acids that underpin all life on Earth.
Scientists have already theorized about life using sulfur compounds, organoborates, or silicon-based chemistry in environments as alien as the sulfuric acid clouds of Venus.
“We suggest that it’s unlikely that every behaviorally sophisticated species in the Universe happened to evolve the same substrate,” the philosophers wrote in the paper.
“Even if our substrate is near-optimal given familiar environmental constraints, the space of possible substrates is large, and other substrates may be favored in other environments with different constraints.”
“In this context, the constraints posed by conditions in the Venusian gas clouds are an example of such environmental constraints, albeit an extreme one: the Venusian environment is almost certainly more different from ours than an environment would need to be to favor life developing in other chemical kinds.”
Most provocatively, the researchers invoke what they call the Copernican Principle of Consciousness.
Just as modern astronomy established that Earth does not occupy a privileged position in the Universe, they argue that we should not assume our planet occupies a uniquely privileged position on the map of consciousness.
If hundreds of behaviorally sophisticated species have arisen across the cosmos in different substrates, there is no principled reason to believe that only those sharing our particular biochemistry are capable of inner experience.
“To think that only entities with our particular architecture would be conscious would be unmotivated terrocentrism,” they wrote.
“Suppose your best guess estimate is that, on Earth, consciousness is present in all vertebrates, plus cephalopods and some insects.”
“And suppose that your best guess estimate is that on average each galaxy contains a million planets where species of approximately that level of behavioral sophistication eventually evolve (even if technological civilizations rarely arise).”
“The observable Universe would then host, over its lifetime, a quintillion (1018) qualifying planets.”
“With that many draws from the lottery, some of these life forms will be strange indeed.”
“We do not think you will then also want to suppose that consciousness will be limited to only those life forms lucky enough to be made of the same substances that compose us here on Earth.”
Inevitably, Professor Schwitzgebel and Dr. Pober raise questions about AI.
However, they stop short of claiming that today’s AI systems are conscious.
In Dr. Pober’s view, we should not assume that today’s computer hardware supports consciousness.
The fact that consciousness could occur in more than one substrate does not suggest that it could occur in every substrate.
“Until we have reason to believe otherwise, we should assume that our current computer chips cannot realize consciousness,” he wrote.
“Not being able to realize consciousness is the default property we attribute to substrates until we have a reason to think otherwise, and our argument does not give us a reason to think otherwise for the substrates of current AI’s.”
Professor Schwitzgebel is somewhat more open to the possibility.
Once the idea that consciousness requires human biology is abandoned, it becomes harder to justify excluding silicon-based systems solely because they are made of silicon.
In any case, he believes this part of the philosophical debate has been too narrow.
“We should be open to the possibility of AI consciousness,” he wrote.
“Once we acknowledge that consciousness does not require our particular substrate, it seems unmotivated to draw the line in any one specific place, as long as the substrate in question shows the capacity to support sufficient behavioral sophistication.”
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Jeremy Pober & Eric Schwitzgebel. 2026. Substrate Flexibility and the Copernican Principle of Consciousness
