J. R. R. Tolkien argued that for an audience to believe in a created story-world, it must possess the ‘inner consistency of reality’: an internally coherent set of laws, histories and conditions that sustains the reader’s belief in that world’s viability. 

While readers and viewers have always been quick to identify contradictions, even in works they adore, the best story-worlds take pains to avoid such challenges to credibility. In contemporary multimedia franchises, controlling the detail of an imaginary universe becomes increasingly difficult. 

The idea of ‘canon’ is, at least in part, an attempt to establish such control: for example, over the internal consistency of the vast Star Wars universe.