Rational belief is the notion that we can somehow be entitled to hold certain beliefs while other propositions ought to be disavowed or held in a state of uncertainty. For our own sanity, we often check our own beliefs against others. For instance, mentally healthy people tend to develop connections with other people outside of the family. These sorts of relationships are useful for measuring our own sense of who we are against external reactions to who we are perceived to be. When we lose this grounding we can become lost in delusions and other forms of distorted thinking that can have all too real consequences, such as depression.
But what exactly is a rational belief? Atheists can look down at Christians as irresponsible with regard to the search for truth and the Christian scriptures describe unbelievers as fools. Who is correct?
Philosophers have reflected on this problem for centuries. My own take on the problem is that we may want to question the very notion of needing to be rational in our beliefs. Let me be clear: we do need to check our beliefs about ourselves, others and the world against the facts. But what that need indicates is a need for self-knowledge. Knowledge of the self entails knowledge of the world and others. Philosophers actively engage in critical self-reflection.