A new philosophical study challenges the idea that consciousness requires human-like biology.
What if consciousness has nothing to do with flesh and blood?
The possibility may sound like science fiction, but it is becoming an increasingly serious philosophical question as scientists search for alien life and artificial intelligence grows more sophisticated. A new analysis argues that consciousness may not be unique to Earth’s biology and could, in principle, emerge in life forms built from entirely different materials.
Eric Schwitzgebel, a distinguished professor of philosophy at the University of California, Riverside, and Jeremy Pober, a former UCR graduate student now a postdoctoral researcher at the University of Lisbon, contend that there is little reason to think conscious experience is tied exclusively to carbon-based life. Instead, they argue, consciousness could arise wherever evolution, or something like it, produces the right kind of complex system.
Rather than attempting to define consciousness itself, the researchers begin with the assumption that it is a real phenomenon. From there, they explore a deceptively simple question: Must consciousness depend on the biology found on Earth, or could it take forms unlike anything humanity has ever encountered?
Their paper arrives as debates over conscious artificial intelligence grow more urgent, inspiring both hopeful visions and alarming scenarios. Schwitzgebel and Pober address AI only briefly and do not offer a shared conclusion. In fact, their views differ. Still, their argument leaves room for the possibility that AI could be conscious someday, even if current systems may not be.
The central idea in the paper is “substrate flexibility.” A property is substrate flexible when it can be produced by more than one type of material. A cup, for example, can be made from glass, plastic or many other substances. A book can exist on paper or in digital form. Music can be stored on vinyl or compact discs.
Schwitzgebel and Pober argue that consciousness may work in a similar way.
“The universe may contain minds stranger than we can imagine,” Schwitzgebel said.
High probability of alien life
The observable universe contains roughly 1 trillion galaxies. Astronomers believe planets are common, and most of them likely have environments very different from Earth’s.
For their argument, Schwitzgebel and Pober estimate that at least 1,000 behaviorally sophisticated extraterrestrial civilizations have existed somewhere in the cosmos. They describe that as a conservative number, noting that “one recent survey found median scientific estimates over one civilization per galaxy at some point in that galaxy’s lifetime.”
Astrobiologists have also considered the possibility of life built from materials unlike those used by organisms on Earth. Some have examined alternative amino acids, different solvents, and even other possible chemical structures.
In the book version of “Project Hail Mary,” author Andy Weir, known for grounding his fiction in plausible science, describes an alien with a shell of oxidized minerals, two circulatory systems, mercury blood, steam-powered muscles, and a crystal brain. The being comes from an extremely hot planet with an atmosphere rich in ammonia.
Schwitzgebel and Pober do not claim that such exotic life definitely exists. Their argument is more limited. If life can emerge under a range of chemical conditions, and if the universe offers enormous numbers of chances for life to arise, it would be surprising if every successful evolutionary lineage used exactly the same biochemical ingredients.
The philosophers also point to the wide variety of nervous systems on Earth. Octopuses, bees, and dogs all process information in different ways. Even here, nature has not chosen just one biological design. Elsewhere in the universe, Schwitzgebel and Pober argue, evolution may be just as creative, or even more so.
Copernican principle of consciousness
Their main argument draws on the Copernican tradition in astronomy. Nicolaus Copernicus and later scientists showed that Earth is not the center of the solar system, the solar system is not the center of the galaxy and the Milky Way is not the center of the universe. Each step made humanity seem less cosmically special than people once assumed.
Schwitzgebel and Pober apply that lesson to consciousness. In their view, consciousness is probably not uniquely tied to us either.
If the universe contains many behaviorally sophisticated species with different biological structures, the authors argue, it would be a form of “terrocentrism” to assume that only Earth-like organisms can be conscious. By that, they mean treating Earth life as uniquely privileged without enough justification. They call their idea “the Copernican principle of consciousness.”
They are not saying that every advanced life form must be conscious. Instead, they argue that if consciousness exists among complex, behaviorally sophisticated beings, it would be strange to suppose that only organisms with our biochemical architecture could have it.
For centuries, humans have repeatedly learned that we are less central, less unique, and less privileged than earlier generations believed.
Schwitzgebel and Pober suggest consciousness may follow the same pattern. Rather than being a rare gift limited to one kind of biological machine, it may be a phenomenon that can arise wherever evolution, or a similar process, produces the right forms of complexity.
Where does this leave AI?
The paper inevitably raises questions about AI, though Schwitzgebel and Pober do not argue that today’s AI systems are conscious.
Pober says we should not assume current computer hardware can support consciousness. The fact that consciousness might occur in more than one substrate does not mean it can occur in every possible substrate.
Schwitzgebel is somewhat more open to the idea. If consciousness does not require human biology, he argues, it becomes harder to rule out silicon-based systems simply because they are made of silicon.
Either way, Schwitzgebel thinks this part of the philosophical discussion has been too limited.
“It’s focused too much on whether silicon can duplicate a human brain and not enough on the broader question of what kinds of systems can be conscious,” he said.
In the paper, Schwitzgebel and Pober separate highly specific properties from broader, more general ones. Asking whether human consciousness can exist in another substrate is a very specific question, they argue, because human consciousness may depend on many details of human biology. Consciousness in general is a broader category.
They compare this to the difference between asking whether another animal can exactly reproduce an eagle’s way of flying and asking whether flight can take different forms. Hummingbirds, bats, and insects all fly, but they do not fly in the same way. Consciousness, Schwitzgebel and Pober argue, may likewise appear in many forms without closely resembling human consciousness.
Reference: “Substrate Flexibility and the Copernican Principle of Consciousness” by Jeremy Pober and Eric Schwitzgebel, 28 May 2026.
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