First Point.—The proofs of reason which demonstrate the real presence of Jesus in the Blessed Sacrament are taken from the absurd consequences of the contrary doctrine. If the Protestants are right in declaring that Jesus is in figure and not in reality in the Holy Eucharist, then Christianity—this religion so pure in its moral and so sublime in its dogma, and having all the characters of divinity-- was, from the beginning, the most monstrous and most extravagant religion. It merits justly all the reproaches of superstition, idolatry, and foolishness lavished on paganism. See all the disciples of Christ, foolish victims of error, having at their head their doctors, their venerable prelates, lights of the world by their science and by their virtue, prostrating themselves before bread, which is only a vain image, and adoring it as the Egyptians formerly adored the fruits of their gardens. Calvin, who had come to undeceive the world, merited divine honors much more than Jesus; he should be regarded as the benefactor of humanity, while Jesus would be only an impostor. In fact, either Jesus foresaw the false interpretation which would be given to His words, "This is My body, this is My blood," or He did not foresee it. If He foresaw it, He should have hindered it otherwise He has deceived His apostles, His friends, and His Church. He has left her in error during fifteen centuries, and He has failed in His promises of being with her to the end of time. If He did not foresee those false interpretations, He is not God; He is only a cheat and an impostor. And thus the denial of the Real Presence carries with it the denial of all religion. These monstrous consequences should suffice to make us reject as false and impious the doctrine which begets them. But these are not all. By the interpretation of Protestants, St. Paul is convicted of absurdity. In his First Epistle to the Corinthians he formally declares that he is guilty of outrage against the body of Jesus who should dare to receive the eucharistic bread unworthily. Are these words, which are so true in a Catholic sense, anything else than an absurdity in the Protestant sense? If Jesus is not really in the Eucharist, or if He is there only in figure, or if the bread is eaten only in faith, can he who participates in this mystery unworthily be wanting in respect for Jesus. Does he abuse His goodness ? How are we to understand that such a one outrages the body of Christ? Besides, if it is faith which attracts Jesus in the Eucharist, to the Jew or an unbeliever not having faith the Eucharist is only a piece of ordinary bread; and how can a piece of bread be profaned ?
St. Paul has said that the glory of the Old Law was nothing when compared with the sublimity of the Gospel. By the interpretation of Protestants these words are false. In fact, if the body of the Saviour is not in the Eucharist, all the excellence and advantage are on the side of the manna. This bread falls from heaven; it is prepared by angel hands, wholly miraculous and diversified in an infinity of tastes; it is a figure of Jesus far more worthy and more noble than the material bread made by the hands of men, if this bread even after consecration was only a figure. We must say the same of the ancient sacrifices, and in particular of the paschal lamb, whose blood was an image of the blood of Jesus more natural than wine, and especially a more lively and touching image. Contrary to the words of St. Paul, the Gospel, in this matter, would be inferior to the Old Law and the Church inferior to the synagogue. Reason rejects such a consequence, and it forces us to recognize the Real Presence or to accept the most monstrous absurdities.
Second Point.—The theological proofs are taken from the very words which Jesus employed in the institution of the Blessed Eucharist: "This is My body, this is My blood." Reflect on these words, and say if the Saviour could employ expressions more precise to affirm His real presence. The Protestants who deny it pretend that here the language of Jesus is figurative and that His words must be taken in a metaphorical sense. As if the Saviour had said: "This is the figure of My body; this is the figure of My blood." The falsity of such an interpretation is evident from the very circumstances in which the words were pronounced. Jesus was about to die ; at that solemn moment one shall hardly employ language which is figurative and almost unintelligible, and especially when one speaks to friends who are the depositaries of his last will. The Saviour of the world was making His last will and testament, and He bequeathed to the Church His body and His blood—all that He possessed. The very essence of a last will and testament is that it shall be expressed in clearest terms and exempt from all ambiguity; the law requires that the words of such a testament should be accepted in their natural and literal sense. Has it ever been heard of that the terms of a last will should be interpreted in a figurative sense? But what is the evident meaning of these words: "This is My body, this is My blood"? Is it the meaning which the Church gives them by taking them in their literal sense? Is it the meaning which heretics give them when they assert that they signify, This is the figure of My body ? But how can this last interpretation be justified ? There are in the world two kinds of signs, viz., natural signs and signs of convention. New, a piece of bread has never been the natural sign of a body; on the other hand, there is not in the Gospel a single word which ever fell from the lips of Jesus which has made it a conventional sign. Jesus had warned His disciples that He would speak to them no longer in parables. His words should therefore be accepted in their natural sense, and every other interpretation is purely arbitrary and finds no foundation anywhere. Behold the last will and testament of the Saviour, and the things He has bequeathed us. They are all contained in these words, which assure to the Catholic priesthood the power of renewing, to the end of the world, what He Himself did the first time. "Do this in commemoration of Me." The priest, in virtue of these words pronounced over the bread and the wine, "This is My body, this is My blood," operates this mystery, the substance of the bread and wine disappears, and they become the body and blood of Jesus.
What simplicity, as Bossuet remarks, and what omnipotent power in these few words ! After such assurance on the part of the Saviour, what remains for us to do if not to believe, and adore, and love? He says that it is His body, therefore it is His body; He says that it is His blood, therefore it is His blood ! My Saviour, be forever blessed for this favor! Thou hast wished to be Thyself the inheritance of Thy children, and Thy love knows how to survive death, in discovering the secret of eternalizing Thy presence in the midst of them.
Source: Short Instructions on the Feasts of the Year, Imprimatur 1897