The Cross is held in the highest reverence by Catholics, because it was the instrument of our Savior’s crucifixion. It surmounts our churches and adorns our sanctuaries. We venerate it as the emblem of our salvation. “Far be it from me,” says the Apostle, “to glory save in the cross of our Lord Jesus Christ.”(11) We do not, of course, attach any intrinsic virtue to the Cross; this would be sinful and idolatrous. Our veneration is referred to Him who died upon it. It is also a very ancient and pious practice for the faithful to make on their person the sign of the Cross, saying at the same time: “In the name of the Father, and of the Son, and of the Holy Ghost.” Tertullian, who lived in the second century of the Christian era, says: “In all our actions, when we come in or go out, when we dress, when we wash, at our meals, before retiring to sleep, ... we form on our foreheads the sign of the cross. These practices are not commanded by a formal law of Scripture; but tradition teaches them, custom confirms them, faith observes them.”(12) By the sign of the cross we make a profession of our faith in the Trinity and the Incarnation, and perform a most salutary act of religion. We believe that on Easter Sunday Jesus Christ manifested His divine power by raising Himself to life, and that having spent forty days on earth, after His resurrection, instructing His disciples, He ascended to heaven from the Mount of Olives. On the Feast of Pentecost, or Whitsunday, ten days after His Ascension, our Savior sent, as He had promised, His Holy Spirit to His disciples, while they were assembled together in prayer. The Holy Ghost purified their hearts from sin, and imparted to them a full knowledge of those doctrines of salvation which they were instructed to preach. On the same Feast of Pentecost the Apostles commenced their sublime mission, from which day, accordingly, we date the active life of the Catholic Church. Our Redeemer gave the most ample authority to the Apostles to teach in His name; commanding them to “preach the Gospel to every creature,”(13) and directing all, under the most severe penalties, to hear and obey them: “He that heareth you, heareth Me; and he that despiseth you, despiseth Me. And He that despiseth Me, despiseth Him that sent Me.”(14) And lest we should be mistaken in distinguishing between the true Church and false sects, which our Lord predicted would arise, He was pleased to stamp upon His Church certain shining marks, by which every sincere inquirer could easily recognize her as His only Spouse. The principal marks or characteristics of the true Church are, her Unity, Sanctity, Catholicity, and Apostolicity,(15) to which may be added the Infallibility of her teaching and the Perpetuity of her existence. I shall treat successively of these marks. Chapter II. THE UNITY OF THE CHURCH.