Like many simple questions, this one is difficult for Daniel to answer. 'Why not? I suppose because it puts me in mind of Alchemy. This soul, this extra thing added to the brain, reminds me of the Quintessence that the Alchemists are forever seeking: a mysterious supernatural presence that is supposed to suffuse the world. But they can never seem to find any. Sir Isaac Newton has devoted his life to the project and has nothing to show for it.'