Who Is Right?

Imagine, if you will, that a group of people gathered in a room to discuss the purpose of life. Among the people was a Buddhist, a Muslim, a Hindu, a Christian, a Mormon, and an atheist. Each of the people claimed that their own beliefs were true, yet each of their beliefs were contradictory to the others' beliefs. So who's right? Is it possible that they're all right? Is it possible that they're all wrong? So, how do we know?