That’s a lot harder than what I did. People have had protracted wars over the definition of what it means to be a Christian. And those wars, I might add, in no way settled the issue.
But it is considerably easier to point out beliefs that are not Christian, or even Judeo-Christian. For example, Judeo-Christian religions, including Islam, are monotheistic. A unified God or a unified Trinity God, it still amounts to the same thing, a single God.
A problem arises with the concept of Satan, because it is an easy, wrong, extrapolation to imagine Satan as an “anti-God”, that is separate, opposite and equal to God. Theologians will slap this wrong idea down, and hard, but it leaves us with a dilemma.
There is God, and there is man. But the existence of Satan implies that there is something in between the two, in terms of power. And unlike a monotheistic God, there is no limit to how many entities can exist that are more powerful than man.
But if they are more powerful than us, what sense does it make for us to try and define what they are?
The Catholics tried, creating a very complicated idea of the heavenly host of many orders of angels and other beings. But they likewise fell into the trap of elevating Satan and his minions, who in Hell tried to recreate the appearance of heaven in Hell, as in castles, banquets, and hierarchies.
But this ends up looking silly. Because it is not up to humans to define what it means to be angels or demons. They are beyond us.
Romans 16:17-20Paul's instruction on how to turn away from false teaching: Be wise in what is good and innocent in what is evil.
Now I urge you, brethren, keep your eye on those who cause dissensions and hindrances contrary to the teaching which you learned, and turn away from them. For such men are slaves, not of our Lord Christ but of their own appetites; and by their smooth and flattering speech they deceive the hearts of the unsuspecting. For the report of your obedience has reached to all; therefore I am rejoicing over you, but I want you to be wise in what is good and innocent in what is evil. The God of peace will soon crush Satan under your feet. The grace of our Lord Jesus be with you.
The Athanasian CreedThese are the truth of Scripture laid out to aid in identifying true Christian faith, helping identify false teaching.
(1) Whosoever will be saved, before all things it is necessary that he hold the catholic faith; (2) Which faith except every one do keep whole and undefiled, without doubt he shall perish everlastingly. (3) And the catholic faith is this: That we worship one God in Trinity, and Trinity in Unity; (4) Neither confounding the persons, nor dividing the substance. (5) For there is one Person of the Father, another of the Son and another of the Holy Spirit. (6) But the Godhead of the Father, of the Son, and of the Holy Spirit is all one, the glory equal, the majesty co-eternal. (7) Such as the Father is, such is the Son and such is the Holy Spirit. (8) The Father uncreate, the Son uncreate, and the Holy Spirit uncreate. (9) The Father incomprehensible, the Son incomprehensible, and the Holy Spirit incomprehensible. (10) The Father eternal, the Son eternal, and the Holy Spirit eternal. (11) And yet they are not three eternals, but one eternal. (12) As also there are not three uncreated nor three incomprehensibles, but one uncreated and one incomprehensible. (13) So likewise the Father is almighty, the Son almighty, and the Holy Spirit almighty; (14) And yet they are not three almighties, but one almighty. (15) So the Father is God, the Son is God, and the Holy Spirit is God; (16) And yet they are not three Gods, but one God. (17) So likewise the Father is Lord, the Son Lord, and the Holy Spirit Lord; (18) And yet they are not three Lords, but one Lord. (19) For like as we are compelled by the Christian verity to acknowledge every person by himself to be God and Lord; (20) so are we forbidden by the catholic religion to say: There are three Gods or three Lords. (21) The Father is made of none, neither created nor begotten. (22) The Son is of the Father alone; not made nor created, but begotten. (23) The Holy Spirit is of the Father and of the Son; neither made, nor created, nor begotten, but proceeding. (24) So there is one Father, not three Fathers; one Son, not three Sons; one Holy Spirit, not three Holy Spirits. (25) And in this Trinity none is afore, nor after another; none is greater, or less than another. (26) But the whole three persons are co-eternal, and co-equal. (27) So that in all things, as aforesaid, the Unity in Trinity and the Trinity in Unity is to be worshipped. (28) He therefore that will be saved must thus think of the Trinity.
(29) Furthermore it is necessary to everlasting salvation that he also believe rightly the incarnation of our Lord Jesus Christ. (30) For the right faith is that we believe and confess that our Lord Jesus Christ, the Son of God, is God and man. (31) God of the substance of the Father, begotten before the worlds; and made of the substance of His mother, born in the world. (32) Perfect God and perfect man, of a reasonable soul and human flesh subsisting. (33) Equal to the Father as touching His Godhead, and inferior to the Father as touching His manhood. (34) Who, although He is God and man, yet He is not two, but one Christ. (35) One, not by conversion of the Godhead into flesh, but by taking of the manhood into God. (36) One altogether, not by the confusion of substance, but by unity of person. (37) For as the reasonable soul and flesh is one man, so God and man is one Christ; (38) Who suffered for our salvation, descended into hell, rose again the third day from the dead; (39) He ascended into heaven, He sitteth on the right hand of the Father, God Almighty; (40) From thence He shall come to judge the living and the dead. (41) At whose coming all men shall rise again with their bodies; (42) And shall give account of their own works. (43) And they that have done good shall go into life everlasting, and they that have done evil into everlasting fire. (44) This is the catholic faith, which except a man believe faithfully, he cannot be saved.
The Nicene Creed
I believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible.
And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all worlds; God of God, Light of Light, very God of very God; begotten, not made, being of one substance with the Father, by whom all things were made.
Who, for us men and for our salvation, came down from heaven, and was incarnate by the Holy Spirit of the virgin Mary, and was made man; and was crucified also for us under Pontius Pilate; He suffered and was buried; and the third day He rose again, according to the Scriptures; and ascended into heaven, and sits on the right hand of the Father; and He shall come again, with glory, to judge the quick and the dead; whose kingdom shall have no end.
And I believe in the Holy Ghost, the Lord and Giver of Life; who proceeds from the Father and the Son; who with the Father and the Son together is worshipped and glorified; who spoke by the prophets.
And I believe in one holy catholic and apostolic Church. I acknowledge one baptism for the remission of sins; and I look for the resurrection of the dead, and the life of the world to come. Amen.
The Apostles' Creed
1. I believe in God the Father, Almighty, Maker of heaven and earth.
2. And in Jesus Christ, His only begotten Son, our Lord;
3. Who was conceived by the Holy Spirit, born of the virgin Mary;
4. Suffered under Pontius Pilate; was crucified, dead, and buried; He descended into hell;
5. The third day He rose again from the dead;
6. He ascended into heaven, and sitteth at the right hand of God the Father Almighty;
7. From thence He shall come to judge the living and the dead.
8. I believe in the Holy Spirit.
9. I believe a holy catholic Church, the communion of saints;
10. The forgiveness of sins;
11. The resurrection of the body;
12. And the life everlasting. AMEN.