I have not been so well abused for an age. Barred from scientific work, I should be miserable, if thee were not heaps of other topics that interest me, from Gadarene pigs and Gladstonian psychology upwards. . . . Your paper deals with a problem which has profoundly interested me for years, but which I take to be insoluble. It would need a book for full discussion. The doctrine of the conservation of energy tells neither one way nor the other.
Energy is the cause of movement of body, i.e. things having mass.
States of consciousness have no mass, even if they can be conceded to be movable. Physical causation need not be the only kind of causation, and when Cabanis said that thought was a function of the brain, in the same way as bile secretion is a function of the liver, he blundered philosophically. Bile is a product of the transformation of material energy. By way of a coarse analogy, consider a parallel-sided piece of glass through which light passes. It forms no picture.