Ryland Grace, the lone human survivor in Andy Weir’s Project Hail Mary, isn’t the only mind in the story—his five-limbed, rock-shelled alien companion, Rocky, with a crystal brain and steam-powered muscles, challenges everything we assume about what a thinking being should look like. Now, philosophers Eric Schwitzgebel of the University of California, Riverside, and Jeremy Pober, now at the University of Lisbon, are taking that imaginative leap seriously in a new working paper, arguing that consciousness may not require Earth-style biology at all. In a universe teeming with possibility, minds might arise in forms so alien they defy our current understanding.
Their argument matters at a moment when scientists are searching for life beyond Earth and engineers are debating whether artificial intelligence could ever be conscious. Rather than defining consciousness—an age-old philosophical puzzle—the duo starts from the shared intuition that we recognize it when we see it. The real question, they say, is whether consciousness depends on carbon-based life, DNA, and neural tissue. Their answer: probably not. Drawing on the concept of "substrate flexibility," they note that many properties—like information storage or structural function—can exist across wildly different materials. A book can be paper or pixels; a cup can be glass or plastic. Why not consciousness?
Schwitzgebel and Pober estimate that at least 1,000 behaviorally sophisticated extraterrestrial civilizations have likely existed across the universe, a conservative figure based on median scientific estimates of one such civilization per galaxy over time. Given the vast diversity of planetary environments—many far hotter, colder, or chemically distinct than Earth—it would be surprising, they argue, if evolution everywhere followed the same biochemical path. Life on Earth already shows remarkable variation: octopuses process information through distributed neurons in their arms, bees navigate complex visual landscapes with tiny brains, and dogs experience emotion through olfactory-rich worlds. If such diversity exists on a single planet, the cosmos may harbor even more radical forms of cognition.
Inspired by the Copernican principle—the idea that Earth holds no privileged place in the universe—the philosophers propose a "Copernican principle of consciousness." Just as we once learned we’re not at the center of the solar system, we may need to accept that human-like biology isn’t the only path to subjective experience. Assuming otherwise, they warn, is a form of "terrocentrism"—an unjustified bias toward Earth life. While they don’t claim current AI systems are conscious, their framework leaves open the possibility that machine minds, or mineral-based aliens like Rocky, could one day meet the conditions for awareness.
As the search for life expands—from Europa’s icy oceans to exoplanets light-years away—our definitions of mind may need to stretch just as far. The universe, after all, has always been more inventive than we dare to imagine.