neuron that becomes active whenever Smith’s hand is poked with a needle. But the surgeon is astonished by what he sees next. The same neuron fires just as vigorously when Smith merely watches another patient being poked. It is as if the neuron (or the functional circuit of which it is a part) is empathizing with another person. A stranger’s pain becomes Smith’s pain, almost literally. Indian and Buddhist mystics assert that there is no essential difference between self and other, and that true enlightenment comes from the compassion that dissolves this barrier.
