Look, I'm not Christian or Catholic, so I'm not trying to butt in to your religion and boss it around. I'm also not trying to "tell you" what you believe and boss you personally around.
My problem is that my understanding (and perhaps this will change with this conversation) is that certain doctrines are so central to Christianity that deviance from them would make you a different religion. For example, Christianity teaches one God (although it is a muddied monotheism due to Trinitarianism). If someone (such as the Mormons) came around and said there is more than one god, they would not be considered a heterodox Christian, they would be considered a different religion altogether.
Is not belief in the atoning sacrifice of Jesus one such belief?
The leitmotif of Catholicism is summarised in the traditional axiom: "
In essentials, unity; in non-essentials, liberty; in all things, charity".
But I think your likely essentially right on the 'sacrificial' point: "
This sacrifice of Christ is unique; it completes and surpasses all other sacrifices." (
CCC 614). So the Catechism defines it thusly, but what it does not define is
how one must understand this atonement taking effect and in what way.
If we turn to the Liturgy, the Eucharist - Christ's body and blood - is defined as:
1. A Whole Burnt Offering (Tamid) in the Epiclesis: “Make holy, therefore, these gifts, we pray, by sending down your Spirit upon them like the dewfall so that they may become for us the Body and Blood of our Lord Jesus Christ.”
2. A Bread Offering Eucharistic Prayer III: “You give life to all things and make them holy, and you never cease to gather a people to yourself, so that from the rising of the sun to its setting a pure sacrifice may be offered to your name.” (cf. Mal 1:11)
3. A Peace Offering Communion Rite: Lord Jesus Christ, who said to your Apostles: Peace I leave you, my peace I give you, look not on our sins, but on the faith of your Church, and gracious grant her peace and unity in accordance with your will. (cf. John 14:27)
4. A Sin Offering Communion Rite: Behold the Lamb of God, behold him who takes away the sins of the world. Blessed are those called to the supper of the Lamb. (Cf. John 1:29)
5. A Guilt Offering Eucharistic Prayer I: Remember also, Lord, your servants N. and N., who have gone before us with the sign of faith and rest in the sleep of peace. Grant them, O Lord, we pray, and all who sleep in Christ a place of refreshment, light, and peace. (cf. Council of Trent, Denzinger 1743
There are certainly some
de fide dogmas that are 'essential' (from the Catholic Church's perspective) in defining the parameters of 'orthodox Christianity' not just from heretical branches of the faith but from theologies that seem to fundamentally diverge from the essentials of our religion itself.
I personally accept anyone as a Christian who defines themselves as such, out of charity and respect for conscience, but
doctrinally my Church has a stricter criteria.
One of these non-negotiable essentials for unity is definitely 'monotheism', defined by every single one of the creeds and anathemas of the ecumenical councils as the first and most essential article of Christian belief.
The
Fourth Lateran Council in 1215, for example, proclaimed the Nicene doctrine of the unicity of God having one single, undivided divine essence which each of the three 'hypostases' just
is whole, entire and undivided: three "
distinct manners of subsisting" of that same divine essence, entity, being and mind in relation to Itself, against the heresy attributed to Joachim of Fiore that the Father, Son and Holy Spirit were merely united as a "
collective and analogous, in the way that many persons are said to be one people".
Your reference to the Mormon understanding of the Godhead as a 'union of wills' between three ontological distinct (in essence) divine beings, is the chief reason why my church treats relations with that particular Church as an exercise in
interfaith dialogue rather than intra-Christian
ecumenism. There was a Vatican decree to that effect from the pontificate of John Paul II in 2001:
The Question of the Validity of Baptism conferred in the Church of Jesus Christ of Latter-Day Saints (vatican.va)
The formula used by the Mormons might seem at first sight to be a Trinitarian formula. The text states: "Being commissioned by Jesus Christ, I baptize you in the name of the Father, and of the Son, and of the Holy Spirit" (cf. D&C 20:73). The similarities with the formula used by the Catholic Church are at first sight obvious, but in reality they are only apparent. There is not in fact a fundamental doctrinal agreement.
There is not a true invocation of the Trinity because the Father, the Son and the Holy Spirit, according to the Church of Jesus Christ of Latter-day Saints, are not the three persons in which subsists the one Godhead, but three gods who form one divinity. One is different from the other, even though they exist in perfect harmony (Joseph F. Smith, ed., Teachings of the Prophet Joseph Smith [TPJSI, Salt Lake City: Desert Book, 1976, p. 372)...
As is easily seen, to the similarity of titles there does not correspond in any way a doctrinal content which can lead to the Christian doctrine of the Trinity. The words Father, Son and Holy Spirit, have for the Mormons a meaning totally different from the Christian meaning. The differences are so great that one cannot even consider that this doctrine is a heresy which emerged out of a false understanding of the Christian doctrine. The teaching of the Mormons has a completely different matrix. We do not find ourselves, therefore, before the case of the validity of Baptism administered by heretics, affirmed already from the first Christian centuries, nor of Baptism conferred in non-Catholic ecclesial communities, as noted in Canon 869 §2.
However when it comes to
soteriology, this is a much more 'vexed' and uncertain area, because the Church has not defined any one 'atonement theory' - whether the
Christus Victor of the patristics, Anselm's
satisfaction paradigm, Abelard's
moral influence theory, Girard's memetic model etc. - as the dogmatically necessary way of understanding the doctrine of the believer's salvation in Christ.
Amongst the Fathers, the most common was faith in "Christ as Victor" over death on the cross through the power of eternal resurrection life, paired with the mystical concept of
theosis derived from the Gospel of John ("
John 14:20, “
On that day you will realize that I am in my Father, and you are in me, and I am in you”) and the Second Epistle of Peter ("
that through these you may be partakers of the divine nature, now that you have escaped the corruption in the world caused by evil desires" (
2 Peter 1:4) .
In Catholicism, our liturgy evokes it during the Communion or Eucharistic part of the Mass, when the priest says over the cup: "
By the mystery of this water and wine may we come to share in the divinity of Christ who humbled himself to share in our humanity."
Around the same time as St. Anselm's satisfaction theory, the monk Abelard (the guy who had a love-affair with the nun Heloise) counteracted St. Anselm with his own "exemplar" theory or salvation by way of moral influence model:
Moral influence theory of atonement - Wikipedia.
The moral influence or example theory of the atonement in Christianity, developed or most notably propagated by Abelard (1079-1142),[1][2] [note 1] is an alternative to Anselm's satisfaction theory of atonement.[1] Abelard focussed on changing man's perception of God as not offended, harsh, and judgemental, but as loving.[3] According to Abelard, "Jesus died as the demonstration of God's love," a demonstration which can change the hearts and minds of the sinners, turning back to God.[3][4]
We are barred from believing in the Protestant '
penal substitution' theory, however.
St. Thomas Aquinas teaches, contra penal punishment, that ancient Israelites did not offer 'sacrifices' to God in order to avoid punishment from God, nor did they see the animals offered as a sort of proxy for themselves. Rather, Jews sought by their offerings to turn away from sin and dedicate themselves wholly to God, in order to be in relationship with Him.
So, for Catholics, it's not receiving our punishment in which atonement is made but rather the
good work of Christ's commitment to loving sinful man even in the midst of the malice of his persecutors, hence why Christ's sacrifice is called a "
pleasing aroma" in Ephesians 5:2 (as opposed to the stench of guilt which arouses God's wrath in Calvinism).
On the other hand, the traditional Protestant interpretation of "atonement" is that in which the guilt and punishment due to one person is transferred over to another i.e. from us to Christ on the cross. This Protestant view of atonement is anathema to both Catholic tradition and the Bible (both Testaments). St Thomas writes: "
Christ's Passion was indeed a malefice on His slayers' part; but on His own it was the sacrifice of one suffering out of charity. Hence it is Christ who is said to have offered this sacrifice, and not the executioners" (
ST 3:48:3.3). So Christ, acting as High Priest, offered up his life by refusing to return the hatred of his enemies in the midst of persecution.
