Below is an excerpt from my book, Starting Points.
Knowing God Does Not Mean…
It does not mean merely intellectually acknowledging God’s existence. Every now and then I’ve had someone tell me they believe in God. Thankfully I’ve never responded in an ungodly way, but I have been tempted to say, “Well, that’s fantastic. According to Scripture, that qualifies you to be a… demon.” That’s not exactly a loving or compassionate way to respond to a person. But it is biblically accurate.
James 2:19 says,
You believe that there is one God. Good! Even the demons believe that–and shudder
Even though the verse is true, it just doesn’t seem very pastoral or loving to call someone a demon, does it? My point, of course, is knowing God involves more than mere intellectual affirmation. But let me add that believing God exists is still vital to knowing him. It’s very important. You cannot know God if you do not believe he exists.
Hebrews 11:6 puts it this way,
And without faith it is impossible to please God, because anyone who comes to him must believe that he exists
If all I knew about someone was a few biographical tidbits, I wouldn’t know them the way Jesus is talking about in John 17:3.