The ninth and tenth Psalms are linked together by a nearly perfect acrostic alphabet structure. In addition, the ninth Psalm ends with a Selah (which is unusual), and the tenth Psalm has no superscription (which is unusual in this part of the Psalter). Since they also share some common language, it makes sense to read them together as a matched set composed by David.
In Psalm 9, the aspiring king praises God for His righteous judgment on behalf of those persecuted. In Psalm 10, he turns his attention to a particular kind of persecutor – the practical atheist. It would have been difficult to be a theoretical atheist in ancient Israel. The Tabernacle, the feasts and the sacrifices, the Torah, and the Mosaic Covenant all pointed toward the existence and intervention of Yahweh. The ancient Israelites could not reject these marks of Judaism openly, but they could reject them in their daily life and practice.
The Psalmist refers to this mindset three times in chapter 10 (verses 4, 11, and 13). In each case, the persecutor denies God’s existence and intervention in human affairs, saying to himself, “There is no God.” Verses 5 to 11 describe the inner workings of one who has rejected the existence of God, as well as their motivations. Without the threat of accountability from a higher power, the atheist feels free to take advantage of the weak and powerless.
David never accuses Saul directly in these Psalms, but one is left to wonder if the elder king gave himself over to this kind of practical atheism. Officially, he was God’s representative to the Israelite people. But practically, privately, he found it hard to follow God’s commands. When he was corrected by Samuel the prophet, he was dismissive and defensive, and when given the chance, he killed the whole priesthood at Nob (1 Samuel 15, 22). Everyone else viewed David as a “man after God’s own heart,” but Saul viewed David with murderous rage.
I usually see atheism as a mild form of unbelief, but these two Psalms put it in a much more dangerous category. Atheism tends to drive people toward aggression since it has no respect for a higher power. Practical atheism is especially dangerous because it changes one’s mindset in secret. The church, like ancient Israel, must stand with the Psalmist and call for God to take action on behalf of the afflicted. This may be one of the most powerful apologetics of them all.