Abnormal psychology were thought to be possessed by evil spirits that had to be exercised through religious rituals. If exorcism failed, some authorities advocated steps such as confinement, beating, and other types of torture to make the body uninhabitable by witches, demons, and spirits. The belief that witches, demons, and spirits are responsible for the abnormal behavior continued into the 15th century. Swiss alchemist, astrologer, and physician Paracelsus (1493–1541), on the other hand, rejected the idea that abnormal behaviors were caused by witches, demons, and spirits and suggested that people's mind and behaviors were influenced by the movements of the moon and
Dynamics of the celestial spheres bodies are moved by angelic spirits, which govern and move them. He maintained, instead, that "celestial bodies are moved by their own natural inclinations similar to weight". Just as heavy bodies are naturally moved by their own weight, which is an intrinsic active principle, so the celestial bodies are naturally moved by a similar intrinsic principle. Since the heavens are spherical, the only motion that could be natural to them is rotation. Kilwardby's idea had been earlier held by another Oxford scholar, John Blund (c. 1175–1248). In two slightly different discussions, John Buridan (c.1295–1358) suggested that when God created the