The advent of anesthesia fundamentally altered modern medicine, and its technology is often seen as infallible. However tens of thousands of patients each year in the United States alone wake up at some point during surgery. In working to eradicate this phenomenon, doctors have been forced to confront how little we know about anesthesia’s effects on the brain. But their studies have also led to a question just as pertinent to philosophers: What does it mean to be conscious?

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