(Neue Zürcher Zeitung, July 13, 2024)
Nils Althaus and Mirko Bischofberger
Even insects may be conscious. Yet it is not even clear whether human subjective experience is anything more than an illusion.
The circle of living creatures credited with consciousness has steadily expanded in recent years. Just this April, nearly 300 researchers agreed that there is “a realistic possibility of conscious experience” in all vertebrates and in many invertebrates, including octopuses, crustaceans, and insects. For mammals and birds, they wrote, the evidence of consciousness is even “strong.” Ignoring that possibility when making decisions that affect these animals would be irresponsible, according to the New York Declaration on Animal Consciousness. But while the circle of consciousness is expanding at one end of the animal kingdom, one apparently unshakable assumption remains: that humans are unquestionably conscious. But are we really?
The recently deceased philosopher Daniel Dennett would probably have raised doubts. To the celebrated American thinker, our subjective experience was a kind of illusion. He compared human consciousness to a computer’s user interface. The inner workings of such a machine are far too confusing and complex for us to interact with them meaningfully. So ingenious software engineers created the illusion of a little desk—the “desktop”—tailored to our needs. It allows us to understand and control what is happening inside the computer. Dennett believed consciousness serves a similar purpose: It is a simplified user interface for the real world. Reality bombards us incessantly with information—rays of light and sound waves arriving from every direction and across every frequency, gas particles pelting us at different speeds and from different angles, and thousands of chemical compounds stimulating our olfactory receptors. Consciousness distills this bewildering jumble into a clean, comprehensible version of reality, populated by objects, colors, shapes, and sounds—The Real World for Dummies, so to speak.
Dennett defended his theories eloquently, illustrating them with incisive examples and metaphors, but he failed to persuade everyone. Illusions generally work by deceiving someone. So whom does Dennett’s illusion of consciousness deceive? The true self? Wouldn’t that self need to be conscious in order to be deceived in the first place? Perhaps the greatest problem with Dennett’s theory is that the illusion feels so extraordinarily real to all of us. In a sense, it is more real than all scientific experiments and descriptions combined. Those must first make their way into our consciousness before they can appear real—or unreal—to us at all. Put differently: When we conduct experiments, we do not observe reality itself. What we actually observe is our consciousness presenting us with a representation of reality. Consciousness itself, by contrast, always seems real. David Chalmers, perhaps the most prominent living philosopher of mind, put it this way: “Conscious experience is at once the most familiar thing in the world and the most mysterious.” Familiar because it is the only thing we can experience directly; mysterious because no one truly understands how it works or why it exists.
The fundamental question is not which regions of the brain become active during conscious experience or what signals neurons emit in the process. Chalmers calls that the “easy problem of consciousness,” and science is making steady progress on it. The crucial question is how physical processes can feel like anything at all—the “hard problem of consciousness.” When you stop to think about it, the whole thing is utterly bizarre. Every process in the brain, from electrical signaling to the release of neurotransmitters, could seemingly unfold in exactly the same way without any sentient being experiencing it. Consider disgust: Volatile compounds from moldy yogurt reach our olfactory receptors and trigger nerve impulses that travel to the brain. The brain receives and processes the information, then sends a signal to the facial muscles, which wrinkle the nose. Other nerves activate the muscles around the mouth, making it twist into a grimace, or the muscles in our legs, causing us to step back. All these processes protect us and those around us from the hazardous substances in mold. But they would serve that purpose just as well if no one actually felt disgust—or had any other conscious experience. Seen in this light, it is utterly mysterious why pendulum clocks, waterfalls, and fungi—all of them likewise filled with particles, forces, and processes—are not conscious, while we are.
What does all this mean? And what should we now believe about consciousness in octopuses, crustaceans, and insects if we do not even know whether we ourselves are conscious? For once, the most promising response may be an intellectual sidestep. Perhaps the relevant question is not exactly what consciousness is, but what it is like. There seems to be something that feels good or bad, right or wrong, desirable or undesirable. Whether that something is an illusion or the foundation of the world may not matter very much. Even with the correct theory in our heads, it would still feel exactly the same. In practical terms, we can probably trust that the window through which we perceive the world is real. And every being that possesses such a window deserves our consideration and respect. Dennett’s ghost nevertheless reminds us that even our deepest certainties sometimes rest on shaky ground.