Why do some people think it is impossible to believe in God?

A:

Many people believe in God, so it is clearly possible to do so. If there are people who believe this is not possible, they are simply ignoring reality.

There is a growing number of people who believe that, for them, it is impossible to believe in God. This is a different matter. They have looked at the evidence for God and found it wanting. They realise that God does not really exist and find believing in a non-existent God as something they can not do.