Abstract

Shamans, healers, and doctors have always known that patients may improve even if no real therapy is administered. In the Charmides, Plato noted that to soothe a headache, one needed "a kind of leaf, which required to be accompanied by a charm, and if a person would repeat the charm at the same time he used the cure, he would be made whole; but that without the charm would be of no avail". Similarly, more than two millennia later, Thomas Jefferson observed, "One of the most successful physicians I have even known has assured me that he used more bread pills, drops of colored water, and powder of hickory ashes, than of all other medication put together"; Jefferson famously labeled this...