I am continuing in 1 John 2 and looking at his warnings to the church about false Christians, in particular, antichrists. It is one of the few places in the bible where you see explicit mention of it. Usually people think of Revelation and the idea of a person who somehow comes to dominate the world with great seduction but John shows that there are many antichrists and they are defined by their denial of the incarnation of Jesus as the Son of God. In this passage he is reassuring the brethren that they are of the body of Christ in spite of those individuals leaving the church who appeared to be genuine believers.
They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
1 John 2:19
I think it is important to know to whom John is referring. There is some dispute about that among Christians, especially as it pertains to the debate over whether you can lose your salvation. As I mentioned earlier, the context of the passage indicates that John is talking about antichrists and not just anyone who leaves the church. He later defines these antichrists, in verse 22, as one who denies the Father and denies the Son, as the Christ. If I can speculate then it even seems like this might apply to people who come into the church under false pretenses that go unnoticed by the brethren. It’s important to keep in mind that this epistle is about knowing the true believers from the fake ones.
I believe the point that John is getting at is that fake Christians can look like the real thing and unless we know how to test for it then even true believers can be deceived. The implication of this is that it is possible to make yourself appear to be a genuine believer. While brotherly love is one mark of a Christian, which John spent time on in chapter 1, here the appropriate test is adherence to doctrines that come from Jesus and the apostles. This is yet another reason why Christians must know biblical doctrine.
By the way, that $100 bill up top? It’s a fake.