The fool has said in his heart there is no God. Sounds familiar right? That is because it comes from the book of Psalms: “The fool has said in his heart, ‘There is no God.’ They are corrupt, They have done abominable works, There is none who does good.” (Psalm 14:1) Typically, many people take this verse and apply it to atheism, claiming it teaches, “The atheist is a fool because he says there is no God.” But, that is actually not what the passage is saying. Did you notice that I put the words there is in italics? That was done on purpose. In the actual text, those words are not a part of the original verse. They were supplied to help the verse make more sense. The problem with this is that in some ways, the men who added these words made some mistakes. You might be thinking, “What’s the issue with saying that the fool has said in his heart that there is no God?” Well, let’s talk about what the passage is actually teaching.
#1. The fool has said no to God. Take out the supplied words, and this is what we are left with: The fool has said in his heart no God. Stop for just a moment and think about what that is saying. Despite what God has said to this individual, they determine that they are not going to do it. They tell GOD no. Quite a bold mindset for someone who depends on God to even have the ability to say no. God has given these people a plan to follow, but they buck up against the authority and power of God and tell Him that they are not going to do it.
Tragically, I have at times been the fool, and so have you. All have sinned and fallen short of the glory of God (Romans 3:23), and no one who reaches an age of accountability will avoid that verse. Why did I tell God no? Because I was selfish and wanted to do what I wanted to do instead of what God knows would benefit me the most. That is the tragedy of all of this. God knows what will help me the most, but I will foolishly look at Him in disbelief and say no.
#2. The reasons the fool says no. Look at what the whole verse put together says: “The fool has said in his heart, ‘There is no God.’ They are corrupt, They have done abominable works, There is none who does good.” (Psalm 14:1) What is David saying here? Individuals who tell God no are doing so because they are corrupt. Corruption is defined as, “the action of making someone or something morally depraved or the state of being so.” 
“Morally depraved” sounds a lot like our society today. God says that He values human life, and we slaughter it on the premise that it is not a human just yet (Proverbs 6:17). He says that marriage is to be between a man and woman only (Matthew 19:4), but we have allowed practically any coupling that can be imagined because we think we know better than He does. He tells us that He wants to have a relationship with us and that our part of that is to seek Him with all our hearts (Jeremiah 29:13). But instead, we tell God to seek us. If He catches us at the right time or tragedy, we will run back to Him. This way of thinking is foolish.
Thankfully, fools do not have to stay fools (Romans 6:3-4). If they did, then we would have no hope of getting out of the sins that plague us. Will we stop saying no and start saying yes? Or continue to be the
 New Oxford Dictionary.