Georgiana D. Hedesan brings us right to Paracelsus himself, the celebrated rejecter of the classical tradition in medicine that had stemmed from Hippocrates and Galen. She concentrates on seven writings by Paracelsus in order to try and find how consistent his teachings on poison were, and on what principles they were based. Paracelsus’s basic position is that all diseases are caused by poison of one sort or another, and Hedesan deals with his views on the origin of such poisons in ens astrale, a heavenly infection. Paracelsus is not an easy author, so a careful analysis is needed to understand his theories, and Hedesan’s title indicates the range of fields to which Paracelsus turned: alchemy, potency and imagination. She concludes her analysis by reaffirming the centrality of Christianity to Paracelsus’s thinking about poison.