Once we imagine human behavior around us existing without consciousness, that behavior begins to look more like many behaviors we see in the natural world that we’ve always assumed were nonconscious, such as the obstacle-avoiding behavior of a starfish, which has no central nervous system.9 In other words, when we trick ourselves into imagining that people lack consciousness, we can begin to wonder if we’re in fact tricking ourselves all the time when we deem other living systems—climbing ivy, say, or stinging sea anemones—to be without it.
How do we truly know animals have no consciousness?
