5. When all this is considered there is good reason to fear lest this great perversity may be as it were a foretaste, and perhaps the beginning of those evils which are reserved for the last days; and that there may be already in the world the "Son of Perdition" of whom the Apostle speaks (II. Thess. ii., 3). Such, in truth, is the audacity and the wrath employed everywhere in persecuting religion, in combating the dogmas of the faith, in brazen effort to uproot and destroy all relations between man and the Divinity! While, on the other hand, and this according to the same apostle is the distinguishing mark of Antichrist, man has with infinite temerity put himself in the place of God, raising himself above all that is called God; in such wise that although he cannot utterly extinguish in himself all knowledge of God, he has contemned God's majesty and, as it were, made of the universe a temple wherein he himself is to be adored. "He sitteth in the temple of God, showing himself as if he were God" (II. Thess. ii., 2).

http://www.papalencyclicals.net/Pius10/p10supre.htm