They used to think sleep paralysis was caused by a demon sitting on the sufferer’s chest, its haunches digging into the flesh around the ribs. Now, like everybody, they know better but they still don’t know much. Sleep paralysis is (probably) a panic response, in which a person lies trapped with their mind alert, unable to move their body. The need to free the limbs feels akin to the desperation of drowning, but it’s impossible to translate the thought into action. When I experienced it, I would coach myself, through clenched teeth, to move one finger, then the next, and the next, until I could unite my brain and my body.