Historicity arises from the (sometimes outlandish) notion that the actual facts of history can be accessed and known with the same sort of certainly available to scientific measurements. When its pursuit is applied with rigor to fable, legend, myth, poetry, saga, and ancient hagiography, it largely misses the point.

The marvelous old stories about Saint Joseph of Arimathea are illustrative. Joseph appears in the New Testament and was likely a living, breathing, actual human being. There is a certain historicity to that part of his story.

But Joseph also figures in certain apocryphal writings, penned subsequently to the Gospels, and their historicity is very much in question.

Still later legends have it that St Joseph was sent to Britain by the Apostle Philip to Christianize the Island. He carried with him a staff carved from the True Cross. He landed in the British west country with twelve disciples and planted his staff in the ground and the Glastonbury Thorn grew from it. At the direction of the Archangel Gabriel, they build a daub and wattle church upon which, later, the great Benedictine abbey of Glastonbury is built, where King Arthur is buried.

As E.A. Freeman says, in Avalonian Quest, "We need not believe that the Glastonbury legends are records of facts; but the existence of those legends is a very great fact."