Well, we can hardly access multiple realities simultaneously to do a study of what constitutes reality as opposed to fiction in each, and from within realities, even one such as the City, it's not possible to identify the way in which specific dimensions are connected to one another. Grasping such a concept would involve a scope that would extend far beyond a full lifetime of study. Already, there have been a multitude of minds that have dedicated their lives to this mystery; we may very well understand it some day, but it may be at great risk. I have gradually come to believe that unraveling certain aspects of the nature of reality, gaining the ability to manipulate space and time... these actions can have consequences that cannot always be foreseen.