You should check this out, a theologian has discovered a mathematical-like proof for discovering the true religion, and false ones, and gives the formula. It turns out that this formula can also be used to determine honesty or dishonesty in any kind of group or in individuals, and uses existing laws of logic, arranged in a formulaic easy to use way. This is the best way you can use to repel a cult at your door: post the formula at the side of your door, on a plaque and show you're already informed. Here is the link to the formula: http://truthproof.tk