Yeah, the "two sided coin" existence of the Endless, where their existence as one side of a coin also shapes and defines that other side. I found this story particularly interesting since it depicts dreams literally shaping reality, yet, it's not all that far fetched. Enough people have a dream and work towards a cause, there's very little that will stop that dream from achieving reality. If there's no drive, no vision, it won't happen. We just...well...tend to have dreams that work within the boundaries of what we consider to be plausible.
Death was probably the most obvious example of the two sided coin. It pretty clear when she visits everyone when they're born. However in stories like the high cost of living it states how death is what gives life its value. Thus, death shapes life and gives it meaning.
Well I better stop before I ramble any farther...
As for this story I have a very hard time reading it...I usually have to skip over the first part so I don't have to cry over the thought of drowned kittens. So horrible....