As a Ph.D. in physics, I have to answer your comments, Bruce. First of all, I was not saying that later versions change the meaning of earlier ones. I was saying that later versions may have different meanings. For instance, the story of Hamlet can be traced back to an episode in the history of Denmark by Saxo Grammaticus. But a great deal in Shakespeare's play is not in Saxo.

On the same subject, Bruce, your logic seems to suggest that we not bother to ask whether Shakespeare's Hamlet contains any material on irresolution or what kind of person would pretend to be insane or the power of ideas received from art in influencing our decisions. (The last is something I see as important in the play.) Some of those questions may be undecidable, and heaven knows many have disagreed on them, but anyone staging the play has to address them.

To get back to "folk" music, I don't know whether Tommy Makem has ever commented on his intention in the words of "Four Green Fields". Should my lack of knowledge prevent me from considering that it might be an allegory, or indeed concluding that it is one? I enjoy it much more because of that obvious interpretation. (For those who don't know the song, I believe it's in the DT--and I recommend it.)

What good is speculating on whether some version of Barbara Allen might be an allegory? Well, someone might choose to perform it based on that interpretation, perhaps even talking to the audience about the speculation (but I hope not presenting it as fact) before singing. Or someone might be prompted to write his or her own song describing the relation between England and Scotland as a relation between a man and a woman. Or the discussion might interest someone in learning something about British history.

You mention Niels Bohr as an intellectual, Bruce, and I admire his work in physics greatly. He also believed that everything must be complemented with its opposite--for example, physics must be complemented with poetry.