The Amish do have a faith, as far as I know, all of the sects are rooted in Christianity. But to "be Amish" suggests a lifestyle of simplicity that few are disciplined enough to follow.
They are an interesting group and I do wish that I was more like them, in that they truly live their faith. You will not see the Amish shopping for designer labels, cool gadgets and the latest in technology. I personally knew one who even though he witnessed a crime of theft, would not testify in court, because he did not wish to harm his brother! They are most probably the first ( next to the native American Indian) of the environmentally "green" people!