Psalm 91:14 English Standard Version (ESV) “Because he holds fast to me in love, I will deliver him; I will protect him, because he knows my name.
Being challenged to prove we know God is a difficult thing. It is faith that opens a knowing which goes beyond rational thought.
Know; Knowledge: no, nol’-ej (in Hebrew chiefly yadha?, noun da?ath; in Greek ginosko, oida’ “to know fully,” epiginosko, noun gnosis epignosis): Knowledge strictly is the apprehension by the mind of some fact or truth in accordance with its real nature; in a personal relation the intellectual act is necessarily conjoined with the element of affection and will (choice, love, favor, or, conversely, repugnance, dislike, etc.). Knowledge is distinguished from “opinion” by its greater certainty. The mind is constituted with the capacity for knowledge, and the desire to possess and increase it. The character of knowledge varies with its object. The senses give knowledge of outward appearances; the intellect connects and reasons about these appearances, and arrives at general laws or truths; moral truth is apprehended through the power inherently possessed by men of distinguishing right and wrong in the light of moral principles; spiritual qualities require for their apprehension spiritual sympathy (“They are spiritually judged,” 1 Cor. 2:14). The highest knowledge possible to man is the knowledge of God, and while there is that in God’s infinity which transcends man’s power of comprehension. (Source International Standard Bible Encyclopaedia)
1 Corinthians 2:14 English Standard Version (ESV) The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
Transcendent knowledge of God can only come from God Himself through the presence of the Holy Spirit dwelling in us. Those who do not have the indwelling spirit cannot know and cannot be convinced.
John 17:8 English Standard Version (ESV) For I have given them the words that you gave me, and they have received them and have come to know in truth that I came from you; and they have believed that you sent me.