What is “transubstantiation” (medieval Christian doctrine)?

The story behind the answer

Medieval Catholic teaching held that at the priest’s words of consecration the underlying reality (substance) of bread and wine is changed into Christ’s body and blood, while their sensory properties (taste, appearance) remain. This accounts for a real, ontological change rather than mere symbolism or only a spiritual presence, making the doctrine distinct from other interpretations.

Formally articulated at the Fourth Lateran Council (1215) and philosophically grounded by Thomas Aquinas through Aristotelian ideas of substance and accidents, it shaped medieval piety and liturgy: the elevation of the Host, the feast of Corpus Christi, and Eucharistic processions. Later contrasts sharpened its profile—Zwingli’s symbolism, Calvin’s spiritual presence, and the Lutheran view of Christ present “in, with, and under” the elements. In the Middle Ages, this belief underscored the sacredness of the Mass and the central place of the Eucharist in Christian life.