Dei Filius

Dei Filius is the incipit of the dogmatic constitution of the First Vatican Council on the Catholic faith, which was adopted unanimously, and issued by Pope Pius IX on 24 April 1870.

The constitution set forth the teaching of "the holy Catholic Apostolic Roman Church" on God, revelation and faith.

The papal bull was influenced by the work of Johann Baptist Franzelin, papal theologian to the Council and later cardinal, who had written a great deal on the topic of faith and rationality.

The document begins by observing that '...God, the principle and end of all things, can be known with certainty by the natural light of human reason from created things." However, it then explains that there are other divine truths, the knowledge of which is necessary for salvation, that are beyond the power of natural reason and can only be known through divine revelation.

It also decreed, "If any one shall not receive as sacred and canonical the books of Holy Scripture, entire with all their parts, as the holy Synod of Trent has enumerated them, or shall deny that they have been divinely inspired: let him be anathema."

The draft presented to the Council on 8 March 1870 drew no serious criticism. But a group of 35 English-speaking bishops, who feared that the opening phrase "Sancta Romana Catholica Ecclesia" might be construed as favouring the Anglican Branch Theory, raised objections to this expression, "Holy Roman Catholic Church". They proposed that the word "Roman" be omitted out of concern that use of the term "Roman Catholic" would lend support to proponents of the Branch Theory. While the Council overwhelmingly rejected this proposal, the text was finally modified to read "The Holy Catholic Apostolic and Roman Church".

The opening words "Sancta Romana Catholica Ecclesia", were voted on on three separate dates. On the first occasion, when this chapter alone was considered, two votes concerned the opening words. The first was on a proposal by a few English-speaking bishops to delete the word "romana", thus changing "Sancta Romana Catholica Ecclesia" (The Holy Roman Catholic Church) to "Sancta Catholica Ecclesia" (The Holy Catholic Church). This was overwhelmingly defeated.

The second vote, held immediately afterwards, was on a proposal to insert a comma, so that "Sancta Romana Catholica Ecclesia" (The Holy Roman Catholic Church) would become "Sancta Romana, Catholica Ecclesia" (The Holy Roman, Catholic Church). This too was defeated, though not as overwhelmingly as the first proposal.

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