1 John: True Worship of God

Lottie and I have been reading and re-reading 1 John over the past month or so, and been trying to get our head around the unifying theme of the letter.
I think I've only ever heard one sermon series on this letter and remember being told it was a "book of tests" of the genuineness of our faith. It certainly does contain a number of tests we can apply to ourselves to assess the reality of our claims to belief, but I feel there must be more to it than that.
It seems to me that the verse which most clearly sums up the letter is 1John 3.16, which is one of my favourite in the Bible:

This is how we know what love is: Jesus Christ laid down his life for us. And we also ought to lay down our lives for our brothers and sisters.

So in John's letter, there is a lot about love, a lot about how Jesus Christ reveals God and a lot about how belief shows itself in action. But then the letter finishes rather abruptly and seemingly strangely:

Little children,  keep yourselves from idols.

Usually, the New Testament letter authors start and finish their letters by spelling out the common theme that runs through the letter. But at first sight, this single sentence seems to jar against the rest of the letter. Which made me spend some time thinking about how it fits in.
And on second thought, the final verse made a lot of sense in the context of the opening paragraph of the letter:

That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands... we proclaim also to you

To the Jews, anything that could be seen with the eyes or touched with the hands was an idol. On top of that, the greeks in Ephesus (where John was probably living when he wrote the letter) were surrounded by idols and idol worship. So John wants to make it clear that this thing that he has seen and touched is not an idol - it's a person: Jesus Christ. And he wants to show his readers the difference between idol worship and true worship of the Living God.

So the conclusion I reached is this: 1 John is a letter about true worship: it's about who we worship and how we worship him.

So what does John tell us about who we worship?

• He is a God who has revealed himself (1Jn 1.2)
• He has revealed himself by sending his Son, Jesus Christ into the world (1Jn 1.1)
• Through Jesus we can know God and have a relationship with him (1Jn 1.3, 1Jn 2.13)
• God is light: he is the source of all goodness in the world (1Jn 1.5)
• Through the blood of Jesus shed on the cross, he wipes out sin (1Jn 1.7, 1Jn 2.2)

What does it mean to worship him, according to John?

• To find fulness of joy (1Jn 1.4)
• To confess that we are sinners and we desperately need his forgiveness in Jesus (1Jn 1.8-10)
• To keep his commandments (1Jn 2.3-4), namely:
• To imitate Jesus in the way we live (1Jn 2.6)
• To worship him alone, loving him with all that we are
• To love others (especially his church) with the love that he has shown us (1Jn 2.9-11)