We must believe in God. All people who use their brains must believe in God. We have brains and we are better than other animals so we must believe in God. God created us with intelligence to know what is right. It is the right thing to do - to believe in God. So, as humans, we must believe in God.
According to the Bible, those who are called by God as fools are those who do not believe in God. We are not fool because we have understanding so, we should believe in God because we are people with understanding.
This is a very thoughtful thing for us to consider. We are intelligently designed. It is a very intelligent Creator who designed our being. The human mind was designed by a very intelligent Creator. If we cannot believe that no one design the computer, why would we believe that there is no God. There is God. God created us. It is only a fool that would not believe that someone created the computer. So, in the same way, it is only a fool who will not believe in the existence of God.