Reverend Thomas O’Reilly


  1. [Mark of the Church] Apostolicity is the mark by which the Church of today is recognized as identical with the Church founded by Jesus Christ upon the Apostles.

  2. It is of great importance because it is the surest indication of the true Church of Christ,

  3. it is most easily examined, and it virtually contains the other three marks, namely, Unity, Sanctity, and Catholicity.

  4. Either the word “Christian” or “Apostolic”, might be used to express the identity between the Church of today and the primitive Church.

  5. The term “Apostolic” is preferred because it indicates a correlation between Christ and the Apostles, showing the relation of the Church both to Christ, the founder, and to the Apostles, upon whom He founded it.

  6. “Apostle” is one sent, sent by authority of Jesus Christ to continue His Mission upon earth, especially a member of the original band of teachers known as the Twelve Apostles.

  7. Therefore the Church is called Apostolic, because it was founded by Jesus Christ upon the Apostles.

  8. Apostolicity of doctrine and mission is necessary.

  9. Apostolicity of doctrine requires that the deposit of faith committed to the Apostles shall remain unchanged. Since the Church is infallible in its teaching, it follows that if the Church of Christ still exists it must be teaching His doctrine.

  10. Hence Apostolicity of mission is a guarantee of Apostolicity of doctrine.

  11. St. Irenæus (Adv. Haeres, IV, xxvi, n. 2) says: “Wherefore we must obey the priests of the Church who have succession from the Apostles, as we have shown, who, together with succession in the episcopate, have received the certain mark of truth according to the will of the Father; all others, however, are to be suspected, who separated themselves from the principal succession”, etc.

  12. In explaining the concept of Apostolicity, then, special attention must be given to Apostolicity of mission, or Apostolic succession.

  13. Apostolicity of mission means that the Church is one moral body, possessing the mission entrusted by Jesus Christ to the Apostles, and transmitted through them and their lawful successors in an unbroken chain to the present representatives of Christ upon earth.

  14. This authoritative transmission of power in the Church constitutes Apostolic succession.

  15. This Apostolic succession must be both material and formal;

  16. the material consisting in the actual succession in the Church, through a series of persons from the Apostolic age to the present;

  17. the formal adding the element of authority in the transmission of power. It consists in the legitimate transmission of the ministerial power conferred by Christ upon His Apostles.

  18. No one can give a power which he does not possess.

  19. [Tracing the Mission] Hence in tracing the mission of the Church back to the Apostles, no lacuna can be allowed, no new mission can arise; but

  20. the mission conferred by Christ must pass from generation to generation through an uninterrupt-ed lawful succession.

  21. The Apostles received it from Christ and gave it in turn to those legitimately appointed by them,

  22. and these again selected others to continue the work of the ministry.

  23. Any break in this succession destroys Apostolicity, because the break means the beginning of a new series which is not Apostolic.

  24. [Mission of authoritative teaching] “How shall they preach unless they be sent?” (Romans 10:15).

  25. An authoritative mission to teach is absolutely necessary, a man-given mission is not authoritative.

  26. Hence any concept of Apostolicity that excludes authoritative union with the Apostolic mission robs the ministry of its Divine character.

  27. [Formal Succession never broken.] Apostoli-city, or Apostolic succession, then, means that the mission conferred by Jesus Christ upon the Apostles must pass from them to their legitimate successors, in an unbroken line, until the end of the world.

  28. This notion of Apostolicity is evolved from the words of Christ Himself, the practice of the Apostles, and the teaching of the Fathers and theologians of the Church.

  29. The intention of Christ is apparent from the Bible passages, which tell of the conferring of the mission upon the Apostles. “As the Father hath sent Me, I also send you. (St. John 20:21)

  30. The mission of the Apostles, like the mission of Christ, is a Divine mission; they are the Apostles, or ambassadors, of the Eternal Father.

  31. “All power is given to Me in heaven and on earth. Going, therefore, teach ye all nations; teaching them to observe all things whatsoever I have commanded you, and behold I am with you all days, even to the consummation of the world.” (St Mt 28:18)

  32. This Divine mission is always to continue the same,

  33. hence it must be transmitted with its Divine character until the end of time,

  34. i.e. there must be an unbroken lawful succes-sion which is called Apostolicity.

  35. The Apostles understood their mission in this sense.

  36. St. Paul, in his Epistle to the Romans (x,8-19) insists upon the necessity of Divinely established mission. “How shall they preach unless they be sent?” (x,15).

  37. In his letters to his disciples Timothy and Titus, St. Paul speaks of the obligation of preserving Apostolic doctrine, and of ordaining other disciples to continue the work entrusted to the Apostles. “Hold the form of sound words, which thou hast heard from me in faith and in the love which is in Christ Jesus” (2 Timothy 1:13). “And the things which thou hast heard from me by many witnesses, the same commend to faithful men, who shall be fit to teach others also” (2 Timothy 2:2). “For this cause left I thee in Crete, that thou shouldst set in order the things that are wanting and shouldst ordain priests in every city, as I also appointed thee” (Titus 1:5).

  38. Just as the Apostles transmitted their mission by lawfully appointing others to the work of the ministry, so their successors were to ordain priests to perpetuate the same mission given by Jesus Christ, i.e. an Apostolic mission must always be maintained in the Church.

  39. The writings of the Fathers constantly refers to the Apostolic character of the doctrine and mission of the Church.

  40. See St. Polycarp, St. Ignatius, (Smyrnæans 8), St. Clement of Alexandria, St. Cyril of Jerusalem, St. Athanasius (History of Arianism), Tertullian (Lib. de Praescipt, n. 32, etc).

  41. We quote a few examples which are typical of the testimony of the Fathers.

  42. St. Irenæus (Adv. Haeres, Iiiv, xxvi, n. 2): “Wherefore we must obey the priests of the Church, who have succession from the Apostles,” etc. — quoted above.

  43. St. Clement (Ep. I, ad. Cor., 42-44): “Christ was sent by God, and the Apostles by Christ….They appointed the above-named and then gave them command that when they came to die other approved men should succeed to their ministry.”

  44. St. Cyprian (Ep. 76, Ad Magnum): “Novatianus is not in the Church, nor can he be considered a bishop, because in contempt of Apostolic tradition he was ordained by himself without succeeding anyone.”

  45. Hence authoritative transmission of power, i.e. Apostolicity, is essential.

  46. In all theological works the same explanation of Apostolicity is found, based on the Scriptural and patristic testimony just cited.

  47. Billuart (III, 306) concludes his remarks on Apostolicity in the words of St. Jerome: “We must abide in that Church, which was founded by the Apostles, and endures to this day.:

  48. Mazella (De Relig. et Eccl., 359), after speaking of Apostolic succession as an uninterrupted substitution of persons in the place of the Apostles, insists upon the necessity of jurisdiction or authoritative transmission, thus excluding the hypothesis that a new mission could ever be originated by anyone in the place of the mission bestowed by Christ and transmitted in the manner described.

  49. Billot (De Eccl. Christi, I, 243-275) emphasizes the idea that the Church, which is Apostolic, must be presided over by bishops, who derive their ministry and their governing power from the Apostles.

  50. Apostolicity, then, is that Apostolic succession by which the Church of today is one with the Church of the Apostles in origin, doctrine, and mission.

  51. The history of the Catholic Church from St. Peter, the first Pontiff, to the present Head of the Church, is an evident proof of its Apostolicity, for no break can be shown in the line of succession.

  52. Cardinal Newman (Diff. of Anglicans, 369) says: “Say there is no church at all if you will, and at least I shall understand you; but do not meddle with a fact attested by mankind.” Again (393): “No other form of Christianity but this present Catholic Communion has a pretense to resemble, even in the faintest shadow, the Christianity of antiquity, viewed as a living religion on the stage of the world;” and again, (395): “The immutability and uninterrupted action of the laws in question throughout the course of Church history is a plain note of identity between the Catholic Church of the first ages and that which now goes by that name.”

  53. If any break in the Apostolic succession had ever occurred, it could be easily shown, for no fact of such importance could happen in the history of the world without attracting universal notice.

  54. Regarding questions and contests in the election of certain popes, there is no real difficulty.

  55. In the few cases in which controversies arose, the matter was always settled by a competent tribunal in the Church, the lawful Pope was proclaimed, and he, as the successor of St. Peter, received the Apostolic mission and jurisdiction in the Church.

  56. Again, the heretics of the early ages and the sects of later times have attempted to justify their teaching and practices by appealing to the doctrine of the Catholic Church, or to their early communion with the Catholic Church.

  57. Their appeal shows that the Catholic Church is regarded as Apostolic even by those who have separated from her communion.

  58. [Apostolicity & Unity] Apostolicity is not found in any other Church. This is a necessary consequence of the unity of the Church. If there is but one true Church, and if the Catholic Church, as has just been shown, is Apostolic, the necessary inference is that no other Church is Apostolic. (See above quotations from Newman, “Diff. of Anglicans”, 369, 393.)

  59. All sects that reject the Episcopate, by the very fact make Apostolic succession impossible, since they destroy the channel through which the Apostolic mission is transmitted.

  60. Historically, the beginnings of all these Church-es can be traced to a period long after the time of Christ and the Apostles.

  61. Regarding the Greek Church, it is sufficient to note that it lost apostolic succession by withdrawing from the jurisdiction of the lawful successors of St. Peter in the See of Rome.

  62. The same is to be said of the Anglican claims to continuity (MacLaughlin, “Divine Plan of the Church”, 213; and, Newman, “Diff. of Angl.”, Lecture 12.) for the very fact of separation destroys their jurisdiction.

  63. They have based their claims on the validity of orders in the Anglican Church. Anglican orders, however, have been declared invalid.

  64. But even if they were valid, the Anglican Chur-ch would not be Apostolic,

  65. for jurisdiction is essential to the Apostolicity of mission.

  66. A study of the organization of the Anglican Church shows it to be entirely different from the Church established by Jesus Christ.

O’Reilly, Thomas. “Apostolicity.” The Catholic Encyclopedia. Vol. 1. New York: Robert Appleton Company, 1907. Numbering, emphasis, annotations added in 2023.

Ecclesiastical approbation. Nihil Obstat. March 1, 1907. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York