You can know every fact about a bat's brain and still not know what it's like to be one

Thomas Nagel argued that even a complete physical description of a bat's sonar-based brain — every neuron, every signal — would leave out something essential: the subjective experience of navigating by echolocation. He used it to argue that consciousness has a first-person character that no amount of third-person, objective science can fully capture.

— Thomas Nagel, What Is It Like to Be a Bat? — The Philosophical Review, 1974
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