According to divine illumination, the process of human thought needs to be aided by divine grace. It is the oldest and most influential alternative to naturalism in the theory of mind and epistemology. It was an important feature of ancient Greek philosophy, Neoplatonism, medieval philosophy, and the Illuminationist school of Islamic philosophy.

Medieval philosophy is the philosophy that existed through the Middle Ages, the period roughly extending from the fall of the Western Roman Empire in the 5th century until after the Renaissance in the 13th and 14th centuries. Medieval philosophy, understood as a project of independent philosophical inquiry, began in Baghdad, in the middle of the 8th century, and in France and Germany, in the itinerant court of Charlemagne in Aachen, in the last quarter of the 8th century. It is defined partly by the process of rediscovering the ancient culture developed in Greece and Rome during the Classical period, and partly by the need to address theological problems and to integrate sacred doctrine with secular learning. This is one of the defining characteristics in this time period. Understanding God was the focal point of study of the philosophers at that time, Muslim and Christian alike.