A crisis in the history of dualism came, however, with the growing popularity of mechanism in science in the nineteenth century. According to the mechanist, the world is, as it would now be expressed, ‘closed under physics’. This means that everything that happens follows from and is in accord with the laws of physics. There is, therefore, no scope for interference in the physical world by the mind in the way that interactionism seems to require. According to the mechanist, the conscious mind is