I, for one, do not want to be called a fool. I don’t want to fail this life test because there is something more than just my body that will suffer the consequences. How do I know that God exists? Because I “Believe” the “Truth” of his word, and his existence has been “Justified” though my experiences. Over and over. Since I believe, I can claim the promises of verse 6 – restoration, rejoicing, and gladness!
But beware, Psalm 53 has some strong warnings for those who do not take God seriously. So if you are in the fool camp, please take some time to consider the evidence because God will deliver on his promises/consequences.