"That is because you are used to the ways of Natural Philosophers, who are forever peering at whatever pleases them. There is a kind of arrogance in that, you are unawares of. In other walks of life, one does need leave. And ’tis well we are having this talk en route to Hanging-Sword-Alley. For the ken we are going to is most certainly the sort where, Doc, you do need leave."