We continue to reflect on the  Catechism of the Catholic Church on the Eucharist.

 1375 It is by the conversion of the bread and wine into Christ's body and blood that Christ becomes present in this sacrament. The Church Fathers strongly affirmed the faith of the Church in the efficacy of the Word of Christ and of the action of the Holy Spirit to bring about this conversion. Thus St. John Chrysostom declares:

It is not man that causes the things offered to become the Body and Blood of Christ, but he who was crucified for us, Christ himself. The priest, in the role of Christ, pronounces these words, but their power and grace are God's. This is my body, he says. This word transforms the things offered.

And St. Ambrose says about this conversion:

Be convinced that this is not what nature has formed, but what the blessing has consecrated. The power of the blessing prevails over that of nature, because by the blessing nature itself is changed. . . . Could not Christ's word, which can make from nothing what did not exist, change existing things into what they were not before? It is no less a feat to give things their original nature than to change their nature.

The mystery of the Eucharist is based on the word and intent of Jesus to which we give the consent of faith. Though our senses tell us one thing, the grace of faith acknowledges what is not seen. By the power of the Holy Spirit and the words of Jesus, bread and wine are substantially changed into the Body and Blood of Jesus. This is what he said and did at the Last Supper. It was the confirmation and fulfillment of what he definitively taught earlier. His words and actions do not need an interpretation or accommodation. When he was questioned about his teaching, he responded, "Does this shake your faith in me?" This is the key to our approach to this mystery, faith in Jesus. Lord, I believe. Help my unbelief!