This is a very important question, worthy of at lest 6 pages of comments.
https://www.newadvent.org/cathen/02033b.htm
CATHOLIC ENCYCLOPEDIA: The Athanasian Creed
At various points the author calls attention to the penalty incurred by those who refuse to accept any of the articles therein set down.
The Father Incomprehensible, the Son Incomprehensible, and the Holy Ghost Incomprehensible
So likewise the Father is Almighty, the Son Almighty, and the Holy Ghost Almighty. And yet they are not Three Almighties but One Almighty.
So there is One Father, not Three Fathers; one Son, not Three Sons; One Holy Ghost, not Three Holy Ghosts. And in this Trinity none is afore or after Other, None is greater or less than Another, but the whole Three Persons are Co-eternal together, and Co-equal
Who, then, is the author? The results of recent inquiry make it highly probable that the Creed first saw the light in the fourth century, during the life of the great Eastern patriarch, or shortly after his death
The "damnatory", or "minatory clauses", are the pronouncements contained in the symbol, of the penalties which follow the rejection of what is there proposed for our belief. It opens with one of them: "Whosoever will be saved, before all things it is necessary that he hold the Catholic Faith". The same is expressed in the verses beginning: "Furthermore, it is necessary" etc., and "For the right Faith is" etc., and finally in the concluding verse: "This is the Catholic Faith, which except a man believe faithfully and firmly, he cannot be saved". Just as the Creed states in a very plain and precise way what the Catholic Faith is concerning the important doctrines of the Trinity and the Incarnation, so it asserts with equal plainness and precision what will happen to those who do not faithfully and steadfastly believe in these revealed truths..
From a dogmatic standpoint, the merely historical question of the authorship of the Creed, or of the time it made its appearance, is of secondary consideration. The fact alone that it is approved by the Church as expressing its mind on the fundamental truths with which it deals, is all we need to know.
The murderous history of your Church is quite telling.
(John 16:2, 3) Men will expel you from the synagogue. In fact, the hour is coming when everyone who kills you will think he has offered a sacred service to God. 3 But they will do these things because they have not come to know either the Father or me.
https://www.newadvent.org/cathen/02616a.htm
The Bohemian Brethren are a link in a chain of sects beginning with Wyclif (1324-84) and coming down to the present day. The ideas of the Englishman found favour with Hus, and Bohemia proved a better soil for their growth than England. Both Wyclif and Hus were moved by a sincere desire to reform the Church of their times; both failed and, without intending it, became the fathers of new heretical bodies — the Lollards and the Hussites. The former were persecuted out of existence in England by Catholic rulers;the latter prospered in Bohemia, thanks to royal and national support.The burning of John Hus at the stake for his stubborn adherence to the condemned doctrines of Wyclif (at Constance, 6 July, 1415) was considered an insult to the faith of the Bohemian nation, which, since its first conversion to Christianity, had never swerved from the truth. The University of Prague came boldly forward to vindicate the man and his doctrines; the party which hitherto had worked at reforming the Church from within now rejected the Church's authority and became the Hussite sect. Divisions at once arose amongst its members. Some completely set aside the authority of the Church and admitted no other rule than the Bible;others only demanded Communion under both kinds for the laity and free preaching of the Gospel, with some minor reforms. The former, who met for worship at "Mount Tabor", were called Taborites; the latter received the name of Calixtines, i.e., the party of the Chalice. As long as they had a common enemy to fight they fought together under the leadership of that extraordinary man, John Trocznowski, known as Zizka (the one-eyed), and for fully fifteen years proved more than a match for the imperial armies and papal crusaders sent to crush them. Peace was at length obtained, not by force of arms, but by skilful negotiations which resulted in the "Compactata of Basle" (30 November, 1433). The compact was chiefly due to the concessions made by the Calixtine party; it found little or no favour with the Taborites. The discontent led to a feud which terminated at the Battle of Lippau (30 May, 1434) with the death of Procopius, the Taborite leader, and the almost total extinction of this party. The small remnant, too insignificant to play a role in politics, withdrew into private life, devoting all their energies to religion. In 1457 one section formed itself into a separate body under the name of the "Brethren's Union" (Unitas Fratrum), which is now generally spoken of as the Bohemian Brethren. Their contemporaries coined for them several opprobrious designations, such as Jamnici (cave-dwellers) and Pivnicnici (beerhouse men), Bunzlau Brethren, Picards (corrupted toPickarts), etc.
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