A full seminary degree is required before salvation? Better pick the right school. That could be an expensive mistake. Right?
Notice how I did not offer any commentary to the verse, and yet you asked a question based on a negative assumption (that was outside of the context)?
Anyways, what is the "doctrine" according to the context?
4 "I rejoiced greatly that I found of thy children walking in truth, as we have received a commandment from the Father.
5 And now I beseech thee, lady, not as though I wrote a new commandment unto thee, but that which we had from the beginning, that we love one another.
6 And this is love, that we walk after his commandments. This is the commandment, That, as ye have heard from the beginning, ye should walk in it.
7 For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.
8 Look to yourselves, that we lose not those things which we have wrought, but that we receive a full reward.
9 Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.
10 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed:
11 For he that biddeth him God speed is partaker of his evil deeds."
(2 John 1:4-11).
In other words, 2 John 1:5 says:
And 2 John 1:6 says:
Also, those who do not confess that Jesus is come in the flesh is also a part of the context, as well. This is saying that the Word (GOD) was made flesh. Meaning: We need to do these three things below.
1. Love one another (2 John 1:5).
2. Walk after his commandments (Which is love) (2 John 1:6).
3. Confess that Jesus is COME into the flesh (2 John 1:7 cf. 1 John 4:3).
This is the doctrine. If a person is not abiding in this particular doctrine, or teaching as mentioned by John in 2 John 1:9 (which includes the context I mentioned), then they are not of God.
This is pretty heavy stuff.
Most today that I am aware of do not teach this.
Most teach that all you need is a belief alone on Jesus and that you can sin and still be saved on some level (Which is a breaking of God's commandments). Which means we do not have to love others and we can still be saved. But this is not what the Bible teaches. Jesus Himself said that we have to love God and love our neighbor as a part of eternal life (See Luke 10:25-28). Yes, we are initially and ultimately saved by God's grace through faith (Which is by believing in Jesus), but we are also saved by being faithful to the Lord, too. If not, then we are our own servants and masters and not the Lord's.