The psalm begins by saying that the fool has said in his heart: there is no God. They are corrupt and have done abominable iniquity; there is none who does good. It is a practical folly more than a theory: the person lives as if God did not exist or would not call to account.
God looks down from heaven on the children of man to see if any understand, if any seek after God. Every one has fallen away; together they have become corrupt; there is none who does good, not even one. He asks whether they have no knowledge, those who work evil, who eat up his people as they eat bread and do not call upon God.
There they are in great terror, where there was no terror, for God scattered the bones of him who encamped against his people; they were put to shame, for God rejected them. The psalm ends with a wish: oh, that salvation for Israel would come out of Zion! When God restores the fortunes of his people, Jacob will rejoice and Israel be glad.