"They should consider the testimony of Christ Himself that 'those who are not with Christ are against Him,' and that they disperse unhappily who do not gather with Him. Let them hear
Jerome who, while the Church was torn into three parts by schism, tells us that whenever someone tried to persuade him to join his group he always exclaimed: 'He who is for the
See of Peter is for me.'
-His Holiness, Pope Gregory XVI (Extract from Mirari Vos, Encyclical
On Liberalism and Religious Indifferentism, August 15th, 1832 A.D.)