"The Avalonian Tradition draws its inspiration from British, rather than English, culture. Wales was able to maintain and preserve the culture, language and traditions of Celtic Britain far longer than the rest of England, so we look to Welsh language, literature and folklore to understand the beliefs of the Britons. The Welsh mythic cycle contains the first references to King Arthur, and through him, to Ynys Afallon – the Island of Avalon. Therefore, to discover the Goddess as She has revealed Herself to the Britons, and as She was probably worshiped on Avalon, we must turn to the mythology of Wales. We therefore seek the Goddesses of Avalon in The Mabinogion and its associated legends as this collection of stories represents the surviving corpus of the mythology of the Celtic Britons and as such, is worthy of deep study.
Due to oral tradition, then, the Divinities of the British Celts do not benefit from having their myths written down by those who worshiped Them, as do the Gods of other cultures. We are not inheritors of an intact tradition, and must look between the lines to seek out the symbols that have made the transition from oral to written form, even if those that transcribed them attempted to have them make sense in their own cultural context. It is for this reason that we must immerse ourselves in the study of Celtic culture so that we may piece the bigger picture back together and reclaim what we can of what was.”Source: Sisterhood of Avalon, “The Avalon Tradition”, http://www.sisterhoodofavalon.org/tradition/index.html