We can KNOW we have eternal life. Not have to guess whether it's so.
And you my think ye believe (enough now and forever) and ye may think ye know.
Jesus is still the judge.
Let us read the chapter in context.
1 John 5: 6 This is the one who came through water and blood, 2 Jesus Christ, not by water alone, but by water and blood. The Spirit is the one that testifies, and the Spirit is truth. 7 So there are three that testify, 8 the Spirit, the water, and the blood, and the three are of one accord. 9 If we accept human testimony, the testimony of God is surely greater. Now the testimony of God is this, that he has testified on behalf of his Son. 10 Whoever believes in the Son of God has this testimony within himself. Whoever does not believe God has made him a liar by not believing the testimony God has given about his Son. 11 And this is the testimony: God gave us eternal life, and this life is in his Son. 12 Whoever possesses the Son has life; whoever does not possess the Son of God does not have life.
13 3 I write these things to you so that you may know that you have eternal life, you who believe in the name of the Son of God. 14 And we have this confidence in him, that if we ask anything according to his will, he hears us. 15 And if we know that he hears us in regard to whatever we ask, we know that what we have asked him for is ours. 16 If anyone sees his brother sinning, if the sin is not deadly, he should pray to God and he will give him life. This is only for those whose sin is not deadly. There is such a thing as deadly sin, about which I do not say that you should pray. 17 All wrongdoing is sin, but there is sin that is not deadly. 18 We know that no one begotten by God sins; but the one begotten by God he protects, and the evil one cannot touch him. 19 We know that we belong to God, and the whole world is under the power of the evil one. 20 We also know that the Son of God has come and has given us discernment to know the one who is true. And we are in the one who is true, in his Son Jesus Christ. He is the true God and eternal life. 21 Children, be on your guard against idols.
This passage here is an exhortation. Notice the mixture of - testify, accord, may know, confidence, discernment, etc. This is a rah rah speech, closing out the letter. This is not surety, it is conditional. What do I mean by that?
- 11 And this is the testimony: God gave us eternal life, and this life is in his Son. 12 Whoever possesses the Son has life; whoever does not possess the Son of God does not have life.
Conditional: each man must possess (which is not the same as just believing) the Son.
- 13 3 I write these things to you so that you may know that you have eternal life, you who believe in the name of the Son of God.
Conditional: each must believe in the name of the Son of God before eternal life may be known. It does not say that this is the only prerequisite, just one of them.
- 14 And we have this confidence in him, that if we ask anything according to his will, he hears us. 15 And if we know that he hears us in regard to whatever we ask, we know that what we have asked him for is ours.
This says that He will grant us things only if it is His will. So, we know that He will do things according to His will, but just in fancier language. Not quite a Pauline sales job, but better than average.
- 16 If anyone sees his brother sinning, if the sin is not deadly, he should pray to God and he will give him life. This is only for those whose sin is not deadly. There is such a thing as deadly sin, about which I do not say that you should pray.
Should pray. So if I pray for somebody, then as long as the sin is not deadly, a one time prayer from me will save my brother's worthless carcass, right? Am I the saviour of my brother, in this instance? What if I pray for my brother, and then on the next occasion of him sinning, pray for him again? Is my brother saved twice? Does he go to the second level of Heaven? That is why one must take the verses in context.
- 18 We know that no one begotten by God sins; but the one begotten by God he protects, and the evil one cannot touch him.
Obvious reference to Jesus here, but do those John is writing to get it? Or might they think that it could refer to them? Or is John exhorting them not to sin, with this line referring to behaviours?
- 19 We know that we belong to God, and the whole world is under the power of the evil one. 20 We also know that the Son of God has come and has given us discernment to know the one who is true. And we are in the one who is true, in his Son Jesus Christ. He is the true God and eternal life. 21 Children, be on your guard against idols.
Closing the deal here, and appealing to the sense of Christian community as against the pagans and Jews who do not know the One who is true.