We can know God for one reason only: God has made Himself known. If God had not chosen to do this, we could not have known Him. That is, God is not accessible through our senses, our reason, our experience, or any other means apart from His willingness to be accessible. Our knowledge of God is absolutely dependent upon divine revelation; and not only is He willing to be known, He desires to be known.
From Understanding Theology in 15 Minutes a Day by Daryl Aaron.