The spirit of medieval philosophy, as understood here, is therefore the Christian spirit, which permeates the Greek tradition, working from within and guiding it to produce a worldview, a Weltanschauung, specifically Christian.

There needed to be Greek temples and Roman basilicas for cathedrals to exist; however, whatever the architects of the Middle Ages owe to their predecessors, they differ from them, and the new spirit that made their creation possible is perhaps the same one that inspired both them and the philosophers of their era.

The Spirit of Medieval Philosophy is one of the most significant legacies left by the French philosopher and historian of philosophy Etienne Gilson. In the twenty chapters-lessons included in the book, Gilson, examining with a unique synthetic ability the positions of Christian thinkers, from the Apologists and the Church Fathers to the great figures of medieval Christian thought—mainly the thought of Augustine, Thomas Aquinas, Duns Scotus, Bonaventure, Anslem of Canterbury, Bernard of Clairvaux, etc.—develops the fundamental axes on which Western medieval thought was based and which shaped the distinct Christian view of the world.

The starting point of the "lessons" is the establishment of the concept of Christian and medieval philosophy itself. Gilson defends the autonomy of thought, which is not hindered but benefits from the assistance provided by supernatural Revelation to human knowledge.

In the pages of the book, fundamental issues are developed such as those of being and its necessity, Christian epistemology, love, free will and freedom, law and morality, nature and history.

The Spirit of Medieval Philosophy constitutes in some way a distillation and a summary of medieval thought and Christian philosophy in general, forged by utilizing the philosophical tools offered by ancient Greek thought.