If the Fourth Gospel (named 'John') had been accorded the primacy of authority that it deserves; then Christianity would be understood differently, and much more simply.
Because that Gospel repeats in different words and explains in different ways the core of Jesus's work - which is that Jesus offered us eternal life through belief in him.
I have listed below twenty-nine instances from the 'John' Gospel in which this matter is referenced.
Of course this immediately raises the questions of what is meant by eternal life; and what is meant by believing in Jesus.
Most of the rest of the Gospel provides these explanations - for example that believing in Jesus is like a sheep following a shepherd - that Jesus will lead us to eternal life.
Or that eternal life is a resurrected life and therefore only attainable by passing through the portal of death.
And that this life eternal is qualitatively superior to this mortal life - this indicated by analogies of the life eternal with (for instance) bread, 'meat'/ food, water... but of an inexhaustible and wholly-satisfying nature, beyond anything possible on earth.
But that core message of Jesus Christ's teaching - of life eternal, and that this life eternal comes via Jesus, is emphasized over-and-again.
In the past couple of thousand years, Christianity has been elaborated (and distorted) from this simple core and into a variety of vast and complex systems - often focused on morality and behaviour; and with many and various justifications.
All kinds of other things than life eternal have (in most times and places) become emphasized far more strongly than the core message.
The simple, direct and personal relation between Jesus the Good Shepherd and those who love and wish to follow him, has often been made indirect - mediated by some interpretative source as the church, theology or scripture.
Yet the Fourth Gospel shows us that we can answer the question 'What is Christianity?' or 'What is a Christian?' by a single sentence... Albeit it will probably take many sentences and much honest thinking to clarify what that sentence means - especially in the context of Modern Man whose consciousness and assumptions are so very different from those of the time and place of Jesus.
As Easter approaches - when the complexities of Christianity reach a kind of climax - we might wish to try and keep this core of Jesus's teaching near the front of our minds.
Twenty-nine indications of eternal life
1. That whosoever believeth in him should not perish, but have eternal life.
2. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
3. He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
4. But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
5. And he that reapeth receiveth wages, and gathereth fruit unto life eternal: that both he that soweth and he that reapeth may rejoice together.
6. Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life. Verily, verily, I say unto you, The hour is coming, and now is, when the dead shall hear the voice of the Son of God: and they that hear shall live. For as the Father hath life in himself; so hath he given to the Son to have life in himself; And hath given him authority to execute judgment also, because he is the Son of man.
7. And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.
8. Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me. And ye will not come to me, that ye might have life.
9. Labour not for the meat which perisheth, but for that meat which endureth unto everlasting life, which the Son of man shall give unto you: for him hath God the Father sealed.
10. For the bread of God is he which cometh down from heaven, and giveth life unto the world.
11. And Jesus said unto them, I am the bread of life: he that cometh to me shall never hunger; and he that believeth on me shall never thirst.
12. And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
13. Verily, verily, I say unto you, He that believeth on me hath everlasting life. I am that bread of life.
14. I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
15. Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
16. It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
17. Then Simon Peter answered him, Lord, to whom shall we go? thou hast the words of eternal life.
18. Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.
19. The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly. I am the good shepherd: the good shepherd giveth his life for the sheep.
20. As the Father knoweth me, even so know I the Father: and I lay down my life for the sheep.
21. Therefore doth my Father love me, because I lay down my life, that I might take it again.
22. And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
23. Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live: And whosoever liveth and believeth in me shall never die.
24. Verily, verily, I say unto you, Except a corn of wheat fall into the ground and die, it abideth alone: but if it die, it bringeth forth much fruit. He that loveth his life shall lose it; and he that hateth his life in this world shall keep it unto life eternal.
25. And I know that his commandment is life everlasting: whatsoever I speak therefore, even as the Father said unto me, so I speak.
26. Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
27. Greater love hath no man than this, that a man lay down his life for his friends.
28. As thou hast given him power over all flesh, that he should give eternal life to as many as thou hast given him. And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.
29. But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.