 On the other side, the mechanical philosophy of Descartes, Mersenne and Gassendi played a role on the materialist side of the debate. Insofar as animals could be treated like machines, it became possible for one to argue that humans were sufficiently like other animals that they too could be treated as machines. Thus an immaterial soul could be dispensed with. There were also medical treatises that suggested that matter is active and that the soul dies with the body. There were the works of Hobbes and Spinoza which argued for a materialistic monism. In 1704 John Toland published his Letters to Serena in which he argues that motion is essential to matter. Finally, there was a Christian mortalist strand in Protestantism. One strand of these Christian mortalists claimed to derive their mortalism from scripture alone and urged that the immaterial soul was a Platonic invention that had been foisted on Christianity and should be dispensed with. In England, this movement can be traced back as far as William Tindale in the sixteenth century and included such luminaries as Overton, Milton, and Hobbes. Henry Dodwell, a well respected biblical scholar, was one such figure in this tradition.