In thinking of medieval philosophy, we must consider that we are covering a vast time of around a thousand years including St Augustine of Hippo (ad 354-430) and William of Ockham (c. 1285–1349) and extending until at least the time of the Renaissance. What links the diversity of this period in Western philosophy is the rise to dominance of Christian beliefs.

It would be wrong to conclude that thinkers in the medieval period merely slavishly reiterated Christian dogma. There exists a tension in medieval philosophy between reason and faith (from the Latin fidere, to trust). The distinction, if there is admitted to be one at all, between the reason of philosophy and the faith of theology is that between, respectively, the insights of natural knowledge derived from the natural cognitive powers of the intellect and senses, and the insights of supernatural knowledge derived from divine revelation. The distinction between philosophy and theology in the Middle Ages was often not clear; generally it can be said that whereas philosophy embodied rational arguments based on premises derivable from naturally occurring powers of thought and the logical working out of those premises (particularly from the philosophers of the ancient world, especially Aristotle), theological arguments were based on divine Christian premises derived from God – in particular from the Bible and the opinions of the Church Fathers as collected in Peter Lombard (c. 1100–60), Four Books of Sentences.