Folly is joy to him that is destitute of wisdom; literally, void of heart; i.e. of understanding (Proverbs 10:23). The perverse, self-willed fool finds pleasure in going on his evil way, and exposing the fatuity which he takes for wisdom.
Septuagint, "The ways of the senseless are wanting in intelligence." A man of understanding walketh uprightly; goes the right way. It is implied that the fool goes the wrong way.