As I use them, the metaphores are resources to explain the behaviour of object A in terms of a better known object B. I think that as more aspect of A’s behaviour can be explained using B ‘semantics’, the better the metaphor is. It is inevitable to find divergences between A and B, as soon you can find them, the worst the metaphor is. I’d say, to take the example from the show, that ‘the course of events’ is a poor metaphor because a course means a somewhat fixed route, while the history has not a defined path.
____
Because I have more doubt than certainties in this topic, my possition will change as the discussion progresses.