In our private Facebook group, members of Catholic Women Speak discuss  topics of interest across the wide spectrum of Catholic life and faith, ranging from pastoral and personal insights and struggles to reflections on prayer and spirituality, and theological and ethical questions.

Our membership includes women from many different backgrounds and cultures, including a number of theologians and biblical scholars, church historians, sociologists, literary scholars, etc. When questions of theology or doctrine arise, there is usually somebody qualified to answer these in an informed and scholarly way.

In a recent discussion on the Assumption, one member asked a question about what one “must” believe as a Roman Catholic. Another member who is a specialist in the early Church posted a response which we thought others would find helpful, so we are sharing it here.

We anonymise all posts from our Facebook group to protect the privacy of our members.


According to the Roman Catholic Church, what defines what “must” be believed? Obviously it goes beyond the credal statements. Is there a single authoritative source for what must be believed? Is there much disagreement among Catholic theologians and scholars about what must be believed?

I am somewhat chagrined to realize that after over 16 years of Catholic education, years of teaching Catholic Sunday School, a lot of reading, I can’t answer that question.

But I can’t think of a better place to ask it than right here. We have so many thoughtful scholars in this group, I have already learned so much here, been given so much to think about …


What is traditionally considered to be De Fide (‘Of the Faith’)? Note that pretty much all of this would also be agreed to by high Anglicans and Orthodox, and it is crucial to the understanding of what is De Fide that the Orthodox churches also recognise it as what the Apostles taught.
What is considered De Fide is above all what was defined by the Ecumenical Councils. The understanding is that everything which is De Fide is contained in Scripture in embryo at least: the Ecumenical Councils were not making new dogma, but drawing out and clarifying what was already there. Nor does the Pope have the right to manufacture ‘new’ truth: the understanding is that everything on which the Pope pronounces infallibly was already in the Apostolic tradition, and if you were to ask the Apostles, they would agree that they did intend to imply this as well. The Orthodox only accept the first seven Ecumenical Councils, so everything from later Councils, you could argue, has to be tested against Orthodox tradition piece by piece.
So here goes with the Seven. (I’m not so expert on the later ones, except Lateran IV, and to some extent Trent). As usual, the following is my own take on all this: it can be argued with!

First Council: Nicaea I (325)

This Council picked up what had already been agreed in the preceding centuries about the Trinity: God is Father, Son and Holy Spirit (cf. Mtt 28:19), and God is ‘Almighty and Creator of all things visible and invisible’ and the Son ‘for our salvation came down, and became incarnate and was made man, and suffered, and arose again on the third day, and ascended into heaven, and will come to judge the living and the dead’. What this Creed added was that the Son is ‘the only-begotten, born of the Father, that is of the substance of the Father, God of God, light of light, true God of true God, born, not made, of one substance with the Father, by whom all things were made, which are in heaven and on earth’. It also laid down that it is incompatible with the Faith to say that ‘there was when he [the Son] was not,’ and, ‘Before he was born, he was not,’ or that he was out of non-existence, or of another substance or essence, or that he was changeable or alterable.

Take-home dogma

all of creation is a product of the radical and eternal oneness and equality of God and the Word of God.

Why should I care?

It was a victory against the view that all of creation is built on hierarchy, and for the doctrine that all of creation is built on the great relationship of proper, equal and unbreakable love guaranteed by the unity of essence and nature within the Trinity. As a side note, the unity is essential because it means the Incarnation was not an example of divine child abuse, but was the act of God freely and without constraint becoming a human being out of love for us.

Second Council: Constantinople (381)

This produced the following Creed (popularly known as the ‘Nicene’ creed):

‘We believe in one God, Father omnipotent, maker of heaven and earth, and of all things visible and invisible. And in one Lord Jesus Christ, the only begotten Son of God, born of the Father before all ages, light of light, true God of true God, begotten not made, consubstantial with the Father, by whom all things were made, who for us humans and for our salvation came down and was made flesh by the Holy Spirit and of the Virgin Mary, and became man, and was crucified for us by Pontius Pilate, suffered, and was buried and arose again the third day, according to the Scripture, and ascended into heaven, and sits at the right hand of the Father, and is coming again with glory to judge the living and the dead; of whose kingdom there shall be no end. And in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father, who together with the Father and Son is worshipped and glorified, who spoke through the prophets. In one holy, Catholic, and Apostolic Church. We confess one baptism for the remission of sins. We look for the resurrection of the dead, and the life of eternity to come.’

Take-home dogma

the Holy Spirit is also consubstantial with God and the Word of God.

Why should I care?

God is not just a self-regarding pair of lovers, but exists in eternal dynamic love, poured out in and on creation for our salvation. (I admit I prefer the Western version of this Creed, which says the Holy Spirit proceeds from the Father and from the Son.)

Third Council: Ephesus (431)

This council laid down that Mary is the Mother of God (Theotokos in Greek), and it is contrary to the Faith to deny that she can be called this.

Take-home dogma

God truly became a human being, and didn't just inspire or inhabit someone that already existed. God truly suffered and died.

Why should I care?

God really was one of us, and one with us, and suffered what we suffer. Mary is honoured by Church tradition above all human beings, and this doctrine is the theological guarantee that God saves through women.

Fourth Council: Chalcedon (451)

This Council produced the following Definition of the Creed: ‘We confess one and the same Son, our Lord Jesus Christ, the same perfect in human nature, truly God and the same with a rational soul and a body truly a human being, consubstantial with the Father according to divinity, and consubstantial with us according to human nature, like unto us in all things except sin, [cf. Heb. 4:15]; indeed born of the Father before the ages according to divine nature, but in the last days the same born of the virgin Mary, Mother of God according to human nature; for us and for our deliverance, one and the same Christ only begotten Son, our Lord, acknowledged in two natures, without mingling, without change, indivisibly, undividedly, the distinction of the natures nowhere removed on account of the union but rather the peculiarity of each nature being kept, and uniting in one person and substance, not divided or separated into two persons, but one and the same Son only begotten God Word, Lord Jesus Christ, just as from the beginning the prophets taught about Him and the Lord Jesus Himself taught us, and the creed of our fathers has handed down to us’.

Take-home dogma

the one who saves us is one Christ who is both entirely God and entirely a real human being, body and rational soul.

Why should I care?

God took on and redeemed our entire humanity, body, soul and mind—there is no longer any bit of us that is inherently bad or wrong, even if we are still a bit weak and prone to sin.

Fifth Council: Constantinople II (553)

This Council did not really pronounce any new dogma, but confirmed Chalcedon in a direction more explicitly close to the teaching of Cyril of Alexandria. It also more clearly affirmed the Consubstantial Trinity: ‘If anyone does not confess that (there is) one nature or substance of the Father and of the Son and of the Holy Spirit, and one power and one might, and that the Trinity is consubstantial, one Godhead being worshipped in three subsistences, or persons, let such a one be anathema. For there is one God and Father, from whom are all things, and one Lord Jesus Christ, through whom are all things, and one Holy Spirit, in whom are all things.’

Take-home dogma

We believe in a consubstantial Trinity, three persons in one essence.

Why should I care?

Our salvation is anchored in the unity and community of God, so that God is truly an unbreakable community of Love, as well as three holy relationships and one Creator and lover of creation.

Sixth Council: Constantinople III (680)

Ruled out the claim that Christ had ‘one will and one operation in the dispensation of the Incarnation’.

Take-home dogma

Christ's human will was real - it wasn't simply a cypher or a puppet carrying out the will of God mindlessly.

Why should I care?

The human will was redeemed—obedience to God is not about annihilating the faculty of longing, but of bringing it and letting it be brought into alignment with divine love.

Seventh Council: Nicea II (787)

This council overturned the previous banning of the use of icons, and argued that they were licit and to be honoured. ‘We, continuing in the regal path [i.e.e that of the empress Irene], and following the divinely inspired teaching of our Holy Fathers, and the tradition of the Catholic Church, for we know that this is of the Holy Spirit who certainly dwells in it, define in all certitude and diligence that as the figure of the honored and life-giving Cross, so the venerable and holy images, the ones from tinted materials and from marble as those from other material, must be suitably placed in the holy churches of God, both on sacred vessels and vestments, and on the walls and on the altars, at home and on the streets, namely such images of our Lord Jesus Christ, God and Savior, and of our undefiled lady, or holy Mother of God, and of the honorable angels, and, at the same time, of all the saints and of holy men’.

Take-home dogma

God, having willed to become incarnate, can also be seen imaged in Mary and the Saints, and so Jesus, the angels and saints should be depicted and honoured in homes and in churches.

Why should I care?

God, having become incarnate, is now also imaged in the saints, both women and men, and can be depicted (and should be reverenced) in icons which call Jesus, Mary, the angels and the saints to mind.