There is no need for any questioning, because as long as you stick to reality, with a bit of luck you can have a pretty comfortable life. So, if you have the bit of luck and you are happy about living your comfortable life, better stop reading right now, because I will try to show that all the things people believe may as well be just illusions. Now lets be a bit destructive and dismantle the world around us. Religion comes first, because it tries so hard to provide the certainty and security we are looking for. It is all a well-constructed illusion, which may be demonstrated by the significant differences between major religions which claim that they are universal.
Christians believe that Bible is the Holy Book.
It may be true. But Moslems, they are pretty sure that Holy book is the Koran. You would find it very difficult to persuade them otherwise. The fact that you can't reconcile the dogma of different religions all around the globe shows that religion is just a fiction in our heads. I am not saying that it is a useless fiction, but its dogma can't be taken for granted and everybody should be aware of this simple fact.