I find it very interesting that your comment, an excellent one, is from 1 John 4 on testing spirits.
1 John 4 New Revised Standard Version (NRSV)
Testing the Spirits
4 Beloved, do not believe every spirit, but test the spirits to see whether they are from God; for many false prophets have gone out into the world.
2 By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God,
3 and every spirit that does not confess Jesus is not from God. And this is the spirit of the antichrist, of which you have heard that it is coming; and now it is already in the world.
I suggest that you watch the movie Heaven is for Real or read the book this is based on.
Also I believe that Josh Mc Dowell wrote a two volume set on Evidence That Demands a Verdict where he set out to disprove the Bible and its teachings and found it to be verifiable and true and changed him in the process.
These are just two of the accounts of many who do believe and know. It is up to each of us to decide for ourselves.
I know for myself what is true it is now up to each to decide for them what is true in their mind.