The first sermon is on Psalm 14 and the theme that 'the fool says in his heart, "there is no God."' It is an apologetically driven sermon arguing for why God is a very reasonable belief and that it is fools who deny him, not fools who believe in him.
In the second sermon Lloyd-Jones does something interesting. He goes to Psalm 50 to show a complementary truth. In Psalm 50 the problem is people showing up to offer sacrifices when their hearts aren't in it at all. This is another kind of fool, though more insidious and self-deceived. Lloyd-Jones kicks off his series on the psalms in this way to show with a one-two punch that while God-denying pagans are fools, God-affirming churchgoers whose hearts are not engaged are even greater fools.
It may surprise some of you to hear me, a Christian preacher, saying a thing like this, but I am almost persuaded that the chief problem today is not the problem of people who say there is no God and who are in the world. It is the problem of people who go to the house of God in a purely technical manner. They go there, but why? Because it is the thing to do. They attend a church as a matter of duty.Just when I begin diagnosing in my mind people I know who do this, Lloyd-Jones rightly says:
God knows, we have all been guilty of this; we may still be guilty.--Martyn Lloyd-Jones, Seeking the Face of God: Nine Reflections on the Psalms (Crossway, 2005), 32-33
Why do we come to God's house? What really is the character of our worship when we come to analyze it? Is it not true that in exactly the same way as God's people of old, we feel that we gain merit by doing it?
Probably thousands of people still go to church on Sunday morning, and then they are finished; and they have done it, as it were, so they can go and do anything else they like now--write family letters, play games, read the Sunday newspapers, look at the television, watch some exciting thing here or there. They have been to church on Sunday morning, and that is all.
That was exactly the position of these children of Israel. It was formal, it was mechanical. . . .
Let me repeat: Ten times worse than being outside and saying, 'There is no God at all' is going to God and to His house in a formal manner only.