There is a mystical, in the sense of beyond this life, knowing of God, or knowledge of God. It includes the intellect, and yet is beyond it. One might say in our language, it is in the heart.
In a way, God has made himself known to all, evident through creation, and through human conscience. Because of our sin, however, we suppress the truth about God, of his existence, goodness and greatness.
Of course without God’s “special” revelation we are all lost. We need more than just the prior revelation of himself, called “general.” And we receive this special revelation in and through Jesus, who himself is the fulfillment of God’s blessing to the world through Israel. And by that revelation, through faith, we can see the Father, and are no longer “without hope and without God in the world.”
In a way to know God is like knowing anyone else. It is personal and heart felt. It is a sense even of kinship in God’s great love, the God who is love.
This knowledge again, comes through Jesus, his coming, ministry of the kingdom, death, resurrection, ascension, and the outpouring of the Spirit, as we await his reappearing when he returns to the earth and in the end returns the kingdom to the Father, that God may be all in all.
Knowing God. That is first and fundamental. We need that. God leads us along and helps us come into that knowledge more fully over time. As we continue in the faith that is in and through Jesus. Together in Jesus for the world.