What is canonical? When we say ”XYZ happened” in Tolkien’s world, we are implicitly choosing works which we regard as a canon on which to base that statement. So which works? Books and maps published in JRRT’s lifetime under his supervision are one choice. We might call that the Original Canon. Since JRRT granted his son CJRT absolute authority as literary executor to publish, edit, alter, complete or destroy (!) his unpublished work and he was aware of the Hobbit and LOTR from the start, that principle might be extended to works published by CJRT and presented as finished, broadly consistent histories rather than literary archaeology: the Simarillion, Unfinished Tales, and the three Great Tales books. We might call that the Greater Canon. Reworkings of materials published in the Original or Greater canons, such as Foster’s excellent Complete Guide or Sibley’s forthcoming Downfall of Numenor or Alan Lee’s wonderful paintings, are not in themselves canon but they sit within one. Fan fiction, David Day’s inventions, Peter Jackson’s changes, and Rings of Power’s nonsense is not canonical.