The crucial role of psychological and environmental factors in causing pain in a significant number of patients only recently received attention. As a consequence, there has emerged a sketch plan of pain apparatus with its receptors, conducting fibers, and its standard function which is to be applicable to all circumstances. But... in doing so, medicine has overlooked the fact that the activity of this apparatus is subject to the a constantly changing influence of the mind.

The Management of Pain (1954) Preface to 1st edition