"Christian theism’s fundamental contention is just this, that nothing whatsoever can be known unless God can be and is known"
— Dr. Cornelius Van Til
Looking again at Van Til's quote:
"nothing whatsoever can be known unless God can be and is known"
The argument is as follows:
A. God CAN be known
B. God IS known
C. Therefore, things can be known
If we look at Romans 1:18-25 (ESV quoted below), Paul makes it clear ALL of us KNOW God. Even the Atheist, Pagan, etc who suppresses that truth in their unrighteousness.
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. 19 For what can be known about God is plain to them, because God has shown it to them. 20 For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. 21 For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. 22 Claiming to be wise, they became fools, 23 and exchanged the glory of the immortal God for images resembling mortal man and birds and animals and creeping things.
24 Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves, 25 because they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator, who is blessed forever! Amen.