It depends on your technical description of the word "know."

I know what I need to know to my own satisfaction. I don't need additional "proof."

There is an overlap between the words "know" and "believe."

For me, personally, I know that Jesus is the God who created the universe, and who "has my back" and will look after me and will bring me into his eternal kingdom.

Knowing those things, I can survive my life.

There's a common saying: "It's not what you know, it's who you know."