Without question, Christ is the Chief Cornerstone.
(Isaiah 28:16, Psalm 118:22, Matthew 21:42, Mark 12:1, Luke 20:17, Acts 4:11, 1 Peter 2:6-7)
The Church of scripture is one united ecclesial body (Eph 4:3-4; Eph 4:13-16; Jn 17:21; Mt 16:18) without schismatic divisions (1 Cor 12:25; Rom 16:17; 1 Cor 1:10;
Jude 1:19; Gal 5:20;
3 John 1:9-10), with one teaching for all the churches (Acts 15:22-23,25,28/Acts 16:4-5; 1 Tim 1:3; 1 Cor 1:10; Eph 4:5;
Jude 1:3), and one bishopric authorized of and by the apostles (
Titus 1:5) by the laying on of hands in ordination (Heb 6:2; 2 Tim 1:6; 1 Tim 4:14;
Titus 1:5), sharing ministers back and forth among all churches (1 Cor 16:3; Rom 16:1,3,9,21,23; Phil 2:19,25;
Titus 3:12), receiving one another in fellowship and in greeting (Rom 15:5-7; Rom 16:16; Col 4:10,12,14;
3 John 1:9-10), where excommunication removes individuals from this one body (Matt 18:17;
1 Corinthians 5:1-2,4-5), and which existed from St. Peter and the apostles unto today (Matt 16:18-19; Eph 3:21).
Protestantism, in Contrast, is an endless schism of divisions with multiple different teachings and authority structures, with no effective means of excommunication and no traceable Apostolic Lineage.
Given these two polar opposite church structures, I'm going to side with the Church of Scripture, every time.
Francis is, also without question, the 266th successor of the Prime Minister of the King, Bishop of the Church of Rome, an apostolic Church which appears in our bibles.
With respect, no one doubted the authority of Peter and his successors until after the 1500s. The early Christians believed it and taught it.
The postions of authority in Israel were held within "offices" (Lk 1:8 or Heb 7:5, for example). This continued right on in the offices of the New Israel of the Church. That is,
Christ and the apostles came to build a Church that would exist forever (Eph 3:21; Matt 16:18-19), and that Church had leadership contained in "offices" (1 Tim 3:1,10; Acts 1:20; Rom 11:13, 12:4).
Offices have authority by virtue of their God-ordained existence, not by virtue of the person holding office. Psalm 109:8 affirms the nature of the offices of the Church--i.e., they are "offices," and they exist apart from the individual, and they continue perpetually for as long as the Melchizedek priesthood shall last (i.e., forever).
Apostolic Succession is historical and biblical. It can be traced by history, going all the way back generation by generation to Jesus. This is precisely why the Catholic priesthood is the one Jesus instituted 20 centuries ago. This is NOT at all to say those outside of this order are not Christians, but only to say that
God has created a governmental order to the Church, and this has not been followed by protestants who broke away from the government of the Church and denied it existed any longer since "the papacy became the endtimes antichrist" (as Luther falsely taught). Obviously, the chaos of the protestant world is the result of this breaking away from the ordained Church government instituted by Christ.