Medieval thought engages with and reiterates classical and biblical precedents. Classical ideas of magic as illicit, malevolent, deceitful and potentially harmful, along with biblical emphases on magic as prohibited and pagan or heretical, recur in secular and canon law. Medieval culture also affirms more positive notions of healing, natural magic, which are underpinned by ideas and practices surviving from more local rituals. Familiar ideas of binding magic, sympathy and antipathy, healing rituals, spirits and demons are sustained. In addition, learned notions of natural magic were passed on, to flower from the twelfth century onwards in the study of the occult sciences. Classical texts were reclaimed by their Christian readers, and the traditions of epiphany and encounter with the divine were maintained. There are many analogies between the welldocumented classical tradition and what can be reconstructed of folk belief, in Britain no doubt itself a mixture of (in some areas) Celtic tradition, notions surviving from Roman Britain, Christianised early on, Germanic practices brought by the Anglo-Saxons, and Christian tradition, long re-established by the time vernacular literary texts began to be written. Folk practices are suggested by the kinds of prohibitions found in both secular and canon law and in theological writing, though it is often difficult to disentangle folk and learned tradition. The medieval supernatural is defined by a complex intersection of ideas: providence and divine intervention, angels and demons, the otherworld and the marvellous. These are complemented by an acute sense of the power of natural forces in the cosmos, which may be probed and harnessed. This chapter begins with the writing of St Augustine, in which classical and Christian meet, and which provides the foundation for much medieval thought. Further sections address the prohibitions and penalties against magic found in secular law and canon law, penitentials and handbooks; the prevalent cultural attitudes, ideas and practices suggested by sermons and other writings such as the twelfth-century chronicles; and the development of learned, often clerical, magic.