“For this reason God sends them a strong delusion so that they will believe what is false, so that all will be condemned-those who did not believe the truth but enjoyed unrighteousness.”
1 Thessalonians 2:11-12
What is a delusion? Here is one dictionary definition: "a persistent false belief held in the face of strong contradictory evidence, especially as a symptom of a psychiatric condition."
The truth of God's reality is everywhere in the world. The smallest flower screams of a Creator. The highest heavens declare the Glory of God. It is indeed delusional not to believe in God with a whole world full of evidence of His existence.
God sends a delusion to those who reject the overwhelming truth of Him. They laugh at and deride "believers" for their "blind faith" while they look at the undeniable body of evidence of God and dismiss it altogether.
They do all this because they enjoy unrighteousness!
Here is the delusion God sends. He touches their minds so that they "won't know what is in the bill until they pass it!" It is just one small example of how God rules over even common sense.