It seems clear that St. Paul and St. John speak of the same enemy of the Church, from the similarity of their descriptions. They both say, that the spirit itself was already at work in their day. "That spirit of the Antichrist," says St. John in the text, "is now already in the world." "The mystery of iniquity doth already work," says St. Paul. And they both describe the enemy as characterized by the same especial sin, open infidelity. St. John says, that "he is the Antichrist that denieth the FATHER and the SON:" while St. Paul speaks of him in like manner as "the adversary and rival of all that is called GOD, or worshipped;" that "he sitteth as GOD in the temple of GOD, setting forth himself that he is GOD." In both these passages, the same blasphemous denial of GOD and religion is described; but St. Paul adds, in addition, that he will oppose all existing religion, true or false, "all that is called God, or worshipped."
Two other passages of Scripture may be adduced, predicting the same reckless impiety; one from the eleventh chapter of Daniel: "The king shall do according to his will; and he shall exalt himself and magnify himself above every god, and shall speak marvelous things against the GOD of gods, and shall prosper till the indignation be accomplished.... Neither shall he regard the GOD of his fathers, nor the Desire of women (that is, as it would appear, the Messiah, to be His mother being the especial privilege and object of hope among the Jewish women), nor regard any god-for he shall magnify himself above all."
The other passage is faintly marked with any prophetic allusion in itself, except that all our SAVIOUR'S sayings have a deep meaning, and the Fathers take this in particular to have such. "I am come in MY FATHER'S Name, and ye receive Me not; if another shall come in his own name, him ye will receive." This they consider to be a prophetic allusion to Antichrist, whom the Jews were to mistake for the Christ. He is to come "in his own name." Not from GOD, as even the SON of GOD came, who if any might have come in the power of His essential divinity, not in GOD'S Name, not with any pretence of a mission from Him, but in his own name, by a blasphemous assumption of divine power, thus will Antichrist come.
Musical Selection (An Advent Prayer; Joseph M. Martin; lyrics in video)