Supposedly, a song written by Dylan as a means of musically stating his progression into his "electric" era. It was the final song on Bringing It All Back Home
, an album which featured both acoustic and electric songs.
This is the album that featured both Subterranean Homesick Blues and Mr. Tambourine Man, perhaps to show Dylan's audience what he used to play, and what he was GOING to play. He dragged his hardcore folk audiences (often kicking and screaming, as one can see from Live 1966: The "Royal Albert Hall Concert") into his next stage of musical exploration, and this is said to be the song that signified the beginning of it all. He said it was all over, but in reality, it was only beginning.