Man instinctively knows that there is a God.
The heavens declare the glory of God, and the sky above proclaims his handiwork. Day to day pours out speech, and night to night reveals knowledge. There is no speech, nor are there words, whose voice is not heard. Their voice goes out through all the earth, and their words to the end of the world (
Psalm 19:1-4, ESV).
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For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse. Romans 1:20
However... The atheist, the scoffer.... The meaning of God's word is hidden from him. intentionally.
Proverbs 4:19
The way of the wicked is like darkness;
They do not know over what they stumble.
1 Corinthians 2:14
But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised.
Isaiah 44:18
They do not know, nor do they understand, for He has smeared over their eyes so that they cannot see and their hearts so that they cannot comprehend.
Ezekiel 12:2
“Son of man, you live in the midst of the rebellious house, who have eyes to see but do not see, ears to hear but do not hear; for they are a rebellious house.