According to which, all of Tolkien's work can be understood as a single continuity, no matter the inconsistencies or alterations, having in mind both his early mythological works (eg. Book of Lost Tales) and the later (Lord of the Rings).
For example the theory suggest that the BoLT should be understood to be happened in the middle ages, long after the prehistorical happenings of the books; the Qenya and Goldogrin words and names are medieval evolution of the "earlier" Quenya and Sindarin of the Elder Days.
All inconsistencies can be dismissed by crediting them to errors or misunderstandings of the copyists, including Eriol.
- Essay by David Giraudeau