I like Bob Dylan. I read a bit about this song on the internet, on Wikipedia and on songmeanings.net. So here's my take on it, enlightened by the above sources.
Oh, and here are the lyrics: http://www.lyricinterpretations.com/Bob-Dylan/Gates-of-Eden. Read them first, then come back here.
The general theme of the song is that life sucks, and then you die. To understand what he means by the Gates of Eden, think about Santa Claus. I think all adults have stopped believing in Santa Claus at some point in their lives. So if someone tells you "Only Santa Claus can get you that", he of course means, "You can't have it, sucker." Same thing with Gates of Eden. There is no Eden, implies Dylan by his tone of voice when mentioning it. And when he ends each stanza with "The things you want are only inside the Gates of Eden", he means forget about ever having them.
But there is an added twist to it. When you tell an adult "Go ask Santa Claus for that", you are talking to someone who already knows there is no Santa Claus, and has gotten over the pain of that discovery. But Dylan is doing three things when he says that something is only inside the Gates of Eden.
First, he tells us that, in his opinion, there is no Eden, no Paradise, no magic place either in this life or the next, where everyone lives happily ever after. And his cynical tone of voice, filled with emotion, tells us that this revelation is still fresh with him, and still hurts.
Second he tells us in each stanza that some important thing we are struggling to realize in our lives, be it discovering the truth or achieving some economic utopia or satisfying love, has no hope of being fulfilled. There is no afterlife, and there is no hope of making this life significantly better, either. Life sucks, and then you die.
Thirdly, he wraps this dual message up in the pleasant little postscript that you are a fool for ever imagining otherwise. Go ask Santa Claus for it, you fool who believes in Santa Claus.
The song, stanza by stanza, mocks every important quest people may have in their lives. Fugeddaboutit.
I want to elaborate on one valuable that he mentions, love. Here are the lines:
At dawn my lover comes to me
And tells me of her dreams
With no attempts to shovel the glimpse
Into the ditch of what each one means.
He has a lover, they share a bed, they are close enough to tell each other their dreams at the romantic break of dawn. What could possibly be wrong with this picture?
My personal take is that nothing is wrong, if you know that love won't solve all your problems. Life goes on, with all it's occasional suckiness, yes, but it is made more pleasant by having a loving relationship. But let's see what Dylan has to say.
He says that each dream has a meaning. And he calls that meaning a ditch. I think he is saying here that a dream is the tip of an iceberg. Beneath the dream lies its meaning, a vast world as deep as the dreamer's very personality, very soul. He calls it a ditch as opposed to, say, a deep well, because this is a cynical black song, so everything has to have a black description. It's not a well, it's a ditch.
His lover makes no attempts to fill the ditch, meaning to understand her deeper self, the self not satisfied with watching Gossip Girl and chewing bubble gum. She had a glimpse of her depths when she had her dream, but the shallow girl just let it slide, and did not take advantage of the opportunity to plumb her depths and find out about herself and share this discovery with her lover.
That's the problem with love. It can only go so deep. The girl in Bob's bed didn't even try, but even if she did it wouldn't have changed much. Ultimately we are individuals, and we cannot share our deepest selves with anyone. That's just the way it is, and it hurts.
Ouch. Bob has cast his magic spell, and writing this has put me in a black mood. OK, guys, let's all snap out of it. Bob only showed us one side of the picture. Life doesn't totally suck.