Just from the first two chapters (if you take the book at face value negating its offensive against gnosticism) you will find the criteria for salvation assurance to be astounding.
If First John is primarily a handbook on assurance, then to have assurance you must:
walk in the light (1:5-7)
confess sin (1:8-10)
keep His (Jesus') commandments (2:3)
walk in the same way he walked (2:6)
love your brother (2:9-11)
not love the world (2:15-17)
not sin (3:6)
practice righteousness (3:7)
not practice sin (3:9)
must give to brother in need (3:17)
Love God and observe His commandments (5:2)
Is there anybody willing to stand up and say this list gives them assurance? Really? You love God with all heart soul strength and mind? If you do please let me know in the comments, I would be interested to hear about it.
Unfortunately I believed for a long time, and have taught youth for a number of years that this is the assurance handbook, and I have ran through this thing test by test with many youth while thinking I was doing them a favor. (Please note I am a fan of Paul Washer, and I certainly appreciate his ministry, and the Lord has ministered his word to me through him, but there are some glaring errors with how he handles this book, and how I have handled it in the past.) In Paul Washer's sermon series on this he affirmed that 1 John is the assurance handbook typically by going to 1 John 5:13 as the proof text.
"These things I have written to you who believe in the name of the son of God, so that you may know that you have eternal life."Washer and others, including myself at that time, would state that 5:13 was the purpose statement of the entire letter. Sounds pretty cut and dried does it not? Yet read the whole of chapter 5 leading up to vs 13, it is all about belief in the Son, and receiving the testimony about Him. 1 John 5:13 is not intended to sum the entire letter, but the section preceding it. However, if you want to make 1 John the assurance handbook it is convenient to apply 5:13 to the rest of the letter as it's sole or primary purpose. That is a touch dishonest though because throughout the letter John explicitly states various other purposes for it
1 John 1:4 ESV And we are writing these things so that our joy may be complete.
1 John 2:1-2 ESV My little children, I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous. (2) He is the propitiation for our sins, and not for ours only but also for the sins of the whole world.
1 John 2:12-14 ESV I am writing to you, little children, because your sins are forgiven for his name's sake. (13) I am writing to you, fathers, because you know him who is from the beginning. I am writing to you, young men, because you have overcome the evil one. I write to you, children, because you know the Father. (14) I write to you, fathers, because you know him who is from the beginning. I write to you, young men, because you are strong, and the word of God abides in you, and you have overcome the evil one.
1 John 2:21 ESV I write to you, not because you do not know the truth, but because you know it, and because no lie is of the truth.
1 John 2:26 ESV I write these things to you about those who are trying to deceive you.This letter is laden with reasons for its existence, and to take any of the reasons and make it the primary message of the letter is a mistake. What if you take 1 John 2:12-14 as the absolute reason of the epistle and neglect 5:13, what do you have? You have universalism. What if you take 1 John 2:1 as the absolute reason? You are advocating sinless perfection. What if you take 1 John 1:4 as the absoulte reason? Then it was all about John having joy. You cannot take any of the "write this to you because..." statements to be the absolute purpose of the book.
The focus of this book was to give Christians who had been assaulted with false doctrine assurance that the doctrine they were holding to was true. Doctrine's such as love of the brethren... confession of sin... the authority of Jesus' teaching. The gnostics and antinomians who may have divorced faith from practice need to be exposed for what they were. Those who would be esoteric about god needed exposed. Therefore strong language correlating works and assurance are made, not to cause believers to question there own faith, but to make them steadfast in the doctrine they received and to question the teachings of those who were leaving their fold and potentially taking others with them (1 John 2:19). In fact if you look past the 'test' passages you will see a number of passages that give blanket assurance apart from any actions taken by the believer, take 1 John 2:2 for example. Gnosticism was promoting that God's will could not be known... which is why John is intense on walking in 'light' not darkness, affirming the visible reality of truth as it plays out.
Believers need to be cautious as they read this letter, and know that it is a letter that is on the offensive against the false teachings that was leading people astray, not a blanket letter on assurance of salvation. If you make this letter entirely about assurance you will find that this letter is on the offensive against you to condemn you. Yes, 1 John 5:1-13 is about assurance, but read some of the blanket blessings in there for those who believe, and notice how the first 4 verses are qualified by the following verses:
1 John 5:1-13 ESV Everyone who believes that Jesus is the Christ has been born of God, and everyone who loves the Father loves whoever has been born of him. (2) By this we know that we love the children of God, when we love God and obey his commandments. (3) For this is the love of God, that we keep his commandments. And his commandments are not burdensome. (4) For everyone who has been born of God overcomes the world. And this is the victory that has overcome the world--our faith. (5) Who is it that overcomes the world except the one who believes that Jesus is the Son of God? (6) This is he who came by water and blood--Jesus Christ; not by the water only but by the water and the blood. And the Spirit is the one who testifies, because the Spirit is the truth. (7) For there are three that testify: (8) the Spirit and the water and the blood; and these three agree. (9) If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son. (10) Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son. (11) And this is the testimony, that God gave us eternal life, and this life is in his Son. (12) Whoever has the Son has life; whoever does not have the Son of God does not have life. (13) I write these things to you who believe in the name of the Son of God that you may know that you have eternal life.
I will leave it there for now. Sorry if this post was a snoozer, but a misunderstanding of 1 John leads to despair, and not assurance.