what is this faith

More from Irenaeus on the Christian Faith:

The Church, though dispersed through our the whole world, even to the ends of the earth, has received from the apostles and their disciples this faith: [She believes] in one God, the Father Almighty, Maker of heaven, and earth, and the sea, and all things that are in them; and in one Christ Jesus, the Son of God, who became incarnate for our salvation; and in the Holy Spirit, who proclaimed through the prophets the dispensations of God, and the advents, and the birth from a virgin, and the passion, and the resurrection from the dead, and the ascension into heaven in the flesh of the beloved Christ Jesus, our Lord, and His [future] manifestation from heaven in the glory of the Father "to gather all things in one,"[Eph 1.10] and to raise up anew all flesh of the whole human race, in order that to Christ Jesus, our Lord, and God, and Saviour, and King, according to the will of the invisible Father, "every knee should bow, of things in heaven, and things in earth, and things under the earth, and that every tongue should confess" [Phil 2.10-11] to Him, and that He should execute just judgment towards all; that He may send "spiritual wickednesses," [Eph 6.12] and the angels who transgressed and became apostates, together with the ungodly, and unrighteous, and wicked, and profane among men, into everlasting fire; but may, in the exercise of His grace, confer immortality on the righteous, and holy, and those who have kept His commandments, and have persevered in His love, some from the beginning [of their Christian course], and others from [the date of] their repentance, and may surround them with everlasting glory. (1:10,1)

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The faith always remains one and the same: the one who is able to expound it at great length does not add anything to it, and the one who can say only a little does not thereby diminish it. (1:10,2)