Consciousness likely not unique to earthlings, paper says
Does consciousness depend on flesh and blood? The answer is almost certainly no, according to Eric Schwitzgebel, a distinguished professor of philosophy at the University of California, Riverside. In a new working paper, Schwitzgebel and Jeremy Pober, a former UCR graduate student who is now a postdoctoral researcher at the University of Lisbon, assert that consciousness is likely possible in life forms made of very different stuff. Think of the five-limbed alien with a rocklike exterior in the recent blockbuster movie "Project Hail Mary."
Schwitzgebel and Pober do not attempt to define consciousness; they proceed from the heuristic premise that it's a real and recognizable phenomenon. Instead, they ask a narrower question: Must it be tied to the biology found on Earth?
The paper comes at a time when the question of conscious artificial intelligence looms large, fueling dreams and nightmares. The authors, who touch only briefly on the matter, do not take a firm position either way and, in fact, diverge in their views. But the arguments they advance leave open the possibility that AI could be conscious, though perhaps not in its current form.
At the heart of the paper's argument is the philosophical notion of "substrate flexibility." A property, such as the ability to hold water, is substrate flexible if it can be achieved with different kinds of materials. For example, a cup can be made of glass or plastic, a book can be printed on paper or stored electronically, and music can be encoded on vinyl records or servers.
Consciousness, Schwitzgebel and Pober argue, is also substrate flexible. "The universe may contain minds stranger than we can imagine," Schwitzgebel said.
High probability of alien life
The observable part of the universe contains about 1 trillion galaxies. Astronomers believe the great majority of planets have environments quite different from Earth's.
For the purposes of their argument, Schwitzgebel and Pober estimate that at least 1,000 behaviorally sophisticated extraterrestrial civilizations have existed at some point in the cosmos. It's a conservative estimate, they say, noting that "one recent survey found median scientific estimates over one civilization per galaxy at some point in that galaxy's lifetime."
At the same time, astrobiologists have hypothesized about life made of different biochemicals than those on Earth. They have investigated alternative amino acids and solvents, and even the possibility of different chemical structures.
In the book version of "Project Hail Mary," author Andy Weir, who is known for describing viable, rigorous science in his fiction, introduces readers to an alien with a shell of oxidized minerals, two circulatory systems, mercury blood, steam-powered muscle and a crystal brain. It hails from a superhot planet with an ammonia-saturated atmosphere.
Schwitzgebel and Pober, however, do not claim that exotic life definitely exists. Their point is more modest: If life can arise under a variety of chemical conditions, and if the universe contains vast numbers of opportunities for life to emerge, then it would be surprising if every successful evolutionary lineage converged on exactly the same biochemical building blocks.
On Earth alone, evolution has produced remarkable diversity in nervous systems, the philosophers note. Octopuses, insects and vertebrates process information in different ways. Even among terrestrial organisms, nature has not settled on a single design. Other parts of the universe, they argue, likely display as much creativity, if not more.
Copernican principle of consciousness
The authors' key argument turns on the Copernican tradition in astronomy. The Renaissance polymath Nicolaus Copernicus and his heirs made a humbling series of discoveries: 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. In other words, humanity occupies a less exceptional position in the cosmos than once imagined.
Schwitzgebel and Pober extend this lesson to consciousness: It probably isn't special.
Assuming there are many behaviorally sophisticated species in the universe with different biological structures, the authors argue that it would amount to a form of "terrocentrism"—unjustified treatment of Earth life as uniquely privileged—to believe consciousness belongs only to organisms like us. The authors coin a phrase, "the Copernican principle of consciousness," to describe this idea.
They don't claim, however, that every advanced life form must be conscious. Rather, they argue that if consciousness exists among behaviorally sophisticated beings, it would be strange to think that only organisms sharing our biochemical architecture could possess it.
For centuries, humans have repeatedly discovered that we are less central, less unique and less privileged than we once believed.
It may be that consciousness, too, is not a rare gift bestowed on one particular kind of biological machine, Schwitzgebel and Pober suggest. Instead, it could be a phenomenon capable of appearing wherever evolution—or something like it—produces the right forms of complexity.
Where does this leave AI?
Inevitably, the paper raises questions about AI. However, the authors stop short of claiming that today's AI systems are conscious.
In 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, he says, does not suggest that it could occur in every substrate.
Schwitzgebel is somewhat more open to the possibility. Once the idea that consciousness requires human biology is abandoned, he argues, it becomes harder to justify excluding silicon-based systems solely because they are made of silicon.
In any case, Schwitzgebel believes this part of the philosophical debate has been too narrow.
"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, the authors distinguish between finely specified properties and coarser, or more general, ones. Asking whether human consciousness can exist in another substrate is a highly specific question, they say, because human consciousness may depend on many details of human biology. The broader category of consciousness is coarser.
The distinction resembles the difference between asking whether an eagle's style of flight can be duplicated exactly and whether flight itself can occur in different forms. Hummingbirds, bats and insects all fly, but not in the same way. Likewise, consciousness might appear in many forms without looking exactly like human consciousness, the authors say.
