Any darkening of the mind, disturbance therein, instigation to the lowest or earthly things; together with every disquietude ...

Years after she suffered a head injury, a patient has an unusual complaint: She can’t seem to keep track of one arm and one leg; they’ve begun to do exactly as they please.

How do we hum a tune ‘without thinking’, choose the right footwear, make a joke? An award-winning account traces how this giant jigsaw tethers us to our shared reality.