Dei Filius  was the dogmatic constitution of the First Vatican Council on the Catholic faith. It was adopted unanimously on 24 April 1870 and was influenced by the philosophical conceptions of Johann Baptist Franzelin, who had written a great deal on the topic of faith and rationality.
The draft presented to the Council on 8 March drew no serious criticism. 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, succeeded in having an additional adjective inserted, so that the final text read: "Sancta catholica apostolica romana Ecclesia"
The constitution thus set forth the teaching of the "Holy, Catholic, Apostolic and Roman Church" on God, revelation and faith.