Folly?
Isn’t that more like being foolish or mistaken? If you can’t know what you don’t know, how is that a sin?
God defines foolishness as “the wisdom of this world”:
“… the wisdom of this world is foolishness with God” (1 Corinthians 3:19).
In contrast to heavenly wisdom (James 3:14-17; 1 Corinthians 2:6-7), worldly wisdom exalts self, focuses on the present, trusts the flesh, and relies only on what it can see or do for itself. Although the schools, cultures, governments, religions, and media of this world endorse and promote it, the “wisdom of this world” is nothing but foolishness (Romans 1:22; 1 Corinthians 1:20).
God says that man thinks in his heart (Hebrews 4:12; Matthew 9:4; Proverbs 23:7; Isaiah 10:7). The “thought of foolishness,” therefore, is a heart problem. God also says that as a man “thinketh in his heart, so is he” (Proverbs 23:7). Because his thoughts control him, any man who thinks a “thought of foolishness” must therefore be a fool. The “thought of foolishness,” then, must be the way that a fool thinks in his heart.
How a Fool Thinks
The Bible explains how a fool thinks in his heart:
“THE fool hath said in his heart, There is no God. …” (Psalm 14:1 and 53:1).
“… God is not in all his thoughts” (Psalm 10:4).
A fool thinks in a way that ignores and thus denies the existence of God (Romans 1:21-22), refusing to receive the things of God (1 Corinthians 2:14). His consequent actions acknowledge God no more than do those of an animal (Psalm 73:22). That means, of course, that a man doesn’t have to be an “atheist” to think like one, because any thought that does not include God is an atheistic one!
Jesus told a parable about a rich man whose plans for the future did not include God. For that reason, God called that man a fool.
“But God said to him, Thou fool, this night thy soul is required of thee: then whose shall those things be, which thou hast provided? So is he that layeth up treasure for himself, and is not rich toward God” (Luke 12:20).
this is from:
sluiceboxadventures.com/endtime_messages/Coats5.htm