"Sacrosancta Lateranensis ecclesia omnium urbis et orbis ecclesiarum mater et caput"
(English: "Most Holy Lateran Church, of all the churches in the city and the world, the mother and head.")
Inscription on the façade of the Basilica of St. John Lateran (Rome).
The Fourth Lateran Council (1215 A.D), called by Pope Innocent III, brought the first assembly of the whole Church since the Council of Chalcedon (451 A.D.). This Council included more than one thousand bishops,
abbots and other dignitaries, both ecclesiastical and secular. It was the most important of the Western Medieval general councils.
Provided below is a Confession of Faith (Can. 1) from the sacred Council:
We firmly believe and openly confess that there is only one true God, eternal and immense, omnipotent, unchangeable, incomprehensible,
and ineffable, Father, Son, and Holy Ghost; three Persons indeed but one essense, substance, or nature absolutely simple; the Father (proceeding) from no one, but the Son from the Father only, and the Holy Ghost equally from both, always without beginning
and end. The Father begetting, the Son begotten, and the Holy Ghost proceeding; consubstantial and coequal, co-omnipotent and coeternal, the one principle of the universe, Creator of all things invisible and visible, spiritual and corporeal, who from the beginning
of time and by His omnipotent power made from nothing creatures both spiritual and corporeal, angelic, namely, and mundane, and then human, as it were, common, composed of spirit and body. The devil and the other demons were indeed created by God good by nature
but they became bad through themselves; man, however, sinned at the suggestion of the devil. This Holy Trinity in its common essense undivided and in personal properties divided, through Moses, the holy prophets, and other servants gave to the human race at
the most opportune intervals of time the doctrine of salvation.
And finally, Jesus Christ, the only begotten Son of God made flesh by the entire
Trinity, conceived with the co-operation of the Holy Ghost of Mary ever Virgin, made true man, composed of a rational soul and human flesh, one Person in two natures, pointed out more clearly the way of life. Who according to His divinity is immortal and impassable,
according to His humanity was made passable and mortal, suffered on the cross for the salvation of the human race, and being dead descended into hell, rose from the dead, and ascended into heaven. But He descended in soul, arose in flesh, and ascended equally
in both; He will come at the end of the world to judge the living and the dead and will render to the reprobate and to the elect according to their works. Who all shall rise with their own bodies which they now have that they may receive according to their
merits, whether good or bad, the latter eternal punishment with the devil, the former eternal glory with Christ.
There is one Universal Church
of the faithful, outside of which there is absolutely no salvation. In which there is the same priest and sacrifice, Jesus Christ, whose body and blood are truly contained in the sacrament of the altar under the forms of bread and wine; the bread being changed
(transsubstantiatio) by divine power into the body, and the wine into the blood, so that to realize the mystery of unity we may receive of Him what He has received of us. And this sacrament no one can effect except the priest who has been duly ordained
in accordance with the keys of the Church, which Jesus Christ Himself gave to the Apostles and their successors.
But the sacrament of baptism,
which by the invocation of each Person of the Trinity, namely of the Father, Son, and Holy Ghost, is effected in water, duly conferred on children and adults in the form prescribed by the Church by anyone whatsoever, leads to salvation. And should anyone after
the reception of baptism have fallen into sin, by true repentance he can always be restored. Not only virgins and those practicing chastity, but also those united in marriage, through the right faith and through works pleasing to God, can merit eternal salvation.
"What Catholic Faith Is" By Fr. Michael Müller, C.SS.R
"TCW Statement on Current Situation/Crisis of The Church" (Also see here.)
Universal Testimony of The Fathers on Underground Church