One thing that all Doctor Who fans know, regardless of how long they have been watching the show, is that the Doctor lies. He doesn't necessarily do it to harm people, but it's typically to help them in some way, either by having them stay behind, or telling someone that something is safe when it truly isn't. Think back to your own childhood. Most parents tell their children that Santa Claus, the Easter Bunny, the Tooth Fairy, et al, are all real, which is an an example of a lie that's for the greater good. It gives children the motivation to be good throughout the year under the pretense that some mystical being is keeping an eye on them to make sure they are nice, otherwise they won't receive any gifts. Lesson Learned: While it's still a lie, it goes to show that not all lies are meant to do harm and in some small cases, lying can actually be an OK thing to do.