We don't know for certain what century Buddha was born in or which century he died in (if you look at wikipedia for example, his suggested lifespan is about 80 years anywhere within a 163 year period.
With Boudica, we only know of her from Roman accounts: and even if she did exist, the Romans were not beyond inventing heroic enemies.
The view that William Shakespeare did not write his plays has been a notable view since his time, although I don't think people who think that tend to care argue that Bill himself never existed. But as has also been said, If William Shakespeare did not write his plays, then someone else named William Shakespeare did.
In the case of Buddha and Jesus (religious figures), it is simply meaningful to recognise that they have a philosophy and sayings attributed to them, many of which can be shown to have to have originated elsewhere (for example, Jesus in the New Testament has some lines that exist in Aesop's Fables, an earlier work). It is possible that the bones attributed to Buddha are actually his, and that splinters exist that the Christian Jesus was actually crucified on. But I see no way that this could be verified for certain.
With Boudica, I know to take the Roman accounts with a pinch of salt. With Shakespeare, I do not have any strong reason to doubt his existence.
When Joseph Smith claim to have a vision from the angel Moroni, and when Muhammad claimed to have a revelation from the angel Jibrīl, how truthful should we regard these accounts?
When Xenophon and Plato quote the sayings of Socrates, and refer to events in his life (e.g. fighting in a battle, or engaging in a symposium) to what extent can we be certain that Socrates actually existed? Xenophon and Plato have known inconsistencies, and some instances that are clear mythologising. Xenophon also writes that he was at the famous symposium, when he would have too young to have done so.
How easy is it for the Word to become flesh, for an ideal to later become a reality?
Consider for example in recent history, in the history of the United States the legends regarding Mother Goose, George "I cannot tell a lie" Washington, Paul Revere, Molly Pitcher, Betsy Ross, and Betty Crocker.



Reply With Quote
