The Diamond In The Box & The "F" Word

A guy was holding a strange box that his uncle gave him long ago before he passed away. He said there was a huge diamond inside, but that no one knew how to open the box. I asked him if he had seen this diamond, and he said he hadn't, but he was certain there was a diamond inside because his uncle told him there was, and his uncle was a good honest man. Allegedly, it was a present that a noble king gave his family long ago as a sign of appreciation or something. He even had a copy of a certificate signed by this king that mentions the diamond in the box. I asked him if his uncle met this king, and he said he didn't, that no one from his family that he's talked to have, but that they all knew about the huge diamond in the box. 

Questions To My Religious Friends

Believing in a God and following a religion may be related, but they are two very different things. I can understand to a certain extent why someone would choose to believe in a God or in an afterlife, but it is a little bit harder for me to understand why as fantastic and contradictory as religions can be, people choose to believe in sometimes completely irrational things, things that they learned from other people. 

The following is a set of questions I'd like to ask religious people. Depending on your beliefs, some of the questions may not apply to you, if this is the case, then just ignore the question.