One of which we assume that our most trusted friends and allies will never harm us. If your best friend were to knock on your door, you would most likely let him in with the belief that he meant you no harm. You assume they won't hurt you because you don't see why they would. Nothing tells you that your best friend should want to hurt you. But nothing tells you that your best friend couldn't hurt you. Just because someone has proven to be trustworthy in the past does not necessarily mean that their actions will continue to be equally trustworthy. However, we assume that their actions are actually trustworthy because they habitually behaved in the way we are accustomed to