Thank you David777 for such a thought-provoking post!

The key doctrine that has been left out is, how to get saved.

Not bad Larry, I can seen your thinking this through.
Still this very important doctrine is missing.

Slowly getting closer LionCub.

Does it have to do with this:

Matthew 28:16 Then the eleven disciples went away into Galilee, to the mountain which Jesus had appointed for them. 17 When they saw Him, they worshiped Him; but some doubted. 18 And Jesus came and spoke to them, saying, “All authority has been given to Me in heaven and on earth. 19 Go therefore[c] and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen.

I noticed that one wasn't there either. lol

Hello Giggles4God, yet again you found a remarkable missing doctrine.

Keep up the good work, still you must persevere to find it. It is very, very important.

OK, my next best: That we are justified (made right with) by faith in God through our belief that Jesus Christ is the Son of God; not by works or by a simple confession of the mouth without conviction of the heart. Romans 4:18-25, Romans 10:10, Galatians 3:11-14

Nice try Larry, I am surprised at how many good doctrines were neglected on the internet site of Christian doctrine.

Still this missing doctrine awaits collection.

Just how many Christian doctrines are there, does anyone know?

I see that salvation (justification) is mentioned (through the blood of the Lamb), but not sanctification. What is missing is the truth that our salvation is conditional on many things:our abiding in Christ; our forgiving of others; our loving others as Christ loves us; and many more...bottom line, the infilling of the Holy Spirit Who changes us into the image of Christ. Most essential, for no-one gets to heaven without taking on the life of Christ.

I also disagree with two of those mentioned. You want me to digress from the OP to mention them?

You will not get any argument from me regarding your post.

What you have stated is correct.

But, we are looking for the missing doctrine.

Incidentally, you were extremely close Brakelite, you almost found it.