Blackstone's logic, though, depends on the idea that at some point a view can be arrived at that is objectively correct. If you agree this is realistic, then there is no escaping the idea that even a person who has an interest can come up with this correct argument. Yes, both he himself and whoever listens to him should scrutinize the argument to see if it is not somehow made incorrect by bias. But it may well prove not to be. And then, suddenly, when it is verified as correct, any undue talk about the person's vested interest seems to be rather sad.