Transubstantiation is a central ingredient to the Sacrament of the Eucharist or Holy Communion that goes back to the Passover meal, or the Lord’s Supper, that Christ shared with his disciples before his crucifixion (Mark 14:22-25; Matt. 26:26-29; Luke 22:19; 1 Corinthians 11:24-26).
During the meal, Christ broke bread and said “This is my body”, and then took some wine and said, “This is my blood.” Ever since, Christians have celebrated the Eucharist as an act of worship and remembrance. Over time, however, questions were raised concerning what Christ might have meant when he said that the bread is his body and the wine his blood. How do the bread and wine change into the blood and body of Christ?
A fascinating answer to this perplexing question was provided by the medieval theologian and philosopher Thomas Aquinas (d. 1274) of the thirteenth century CE. Aquinas is remembered fondly as a scholastic thinker who explored the Christian faith logically through an extensive application of Greek thought and philosophy to Christian theology. Aquinas attempted to answer this question through the doctrine or practice of transubstantiation which became the official doctrine and practice of the Roman Catholic Church.
In answer to the question, Aquinas drew on the work of philosopher Aristotle (d. 323 BCE) in an attempt to explain how the “real presence” of Christ could be found in the elements of the bread and wine. He believed that the connection between Christ and the elements is important as without such a link the Eucharist loses its significance. To understand what Aquinas is saying we need to acknowledge the distinction Aristotle made between “substance” and “accidents.” The substance, according to Aristotle, is the unique identity of an object or a person. The accidents are the attributes of the substance and these can change without the identity of the substance changing. For example, a chair might be plastic and red, but if it was steel and blue it would still be a chair. Using Aristotle’s distinction, Aquinas proposed the idea that it is possible for the substance or essence of an object or a person (Christ) to be within the accidents or attributes of other objects. In other words, Christ could be in the bread and wine consumed during the Eucharist. Aquinas claimed that it is possible for one object to be converted into another, which means that when the priest prayed over the wine and bread, their substance literally converted into the blood and body of Christ.
This is why the Sacrament of the Eucharist is the most revered of all sacraments in the Catholic Church. It is revered because it is believed that the “real presence” of Christ is in the elements, despite the attributes of the bread and wine remaining the same. It is through the Eucharist that participants experience the real presence of Jesus Christ.
Trigilio, John., and Brighenti, Kenneth. 2011. Catholicism For Dummies. Hoboken: John Wiley & Sons.