"Having made the Unbreakable Vow, it is impossible for me to engage in motivated reasoning which would put the world at risk, while it is entirely possible for you to do so. I am convinced that you are more likely to fulfill the prophecy by killing me than by letting me live. Since my reasoning is not and cannot be motivated in such a way as to put the world at risk, while yours can be, it is more likely that I am right, and it would be to your advantage not to kill me."