I just finished Sophie's world for the first time and I must say that I am impressed at how well these deep philosophical questions were made understandable. Reading Nietzsche or Kant makes it sound like philosophy is impenetrable to all but the highest brow people.

I have a theory about the ending of the book. The scene when Hilde meets her father and they talk about the book is being overseen by the "angels" of Sophie and Albert. The boat on the dock at Bjerkley comes loose, supposedly, when Sophie focuses all her energy to influence the other reality. I think that Hilde actually loosened the boat herself.

Why?
1. "Supernatural phenomena" like ghosts and telekinesis are effectively debunked in the book. Reality is interesting enough without the need for them.
2. Freud's "Subconscious" shows that we don't always act purely rationally; there are things influencing our lives that we may not see on the surface but are lying in wait "outside the doors of the concert hall."
3. Since Hilde REALLY WANTS TO KNOW what happened to Sophie and Albert after her version of Sophie's World ends, she has inadvertently started planning a new story for them.
4. Sophie was able to make Hilde feel the "gadfly" when she tried to hit her with a wrench, but it DIDN'T work on the major. This signifies that Hilde has taken command of Sophie and Albert's angels, though she may not be doing it consciously.
5. The boat coming loose from the dock is not a new idea. Sophie does not have free will in the sense that she can come up with ideas that have not been given to her by the Major's writing. This "angel" of Sophie will never age and never come up with new ideas unless someone in our world gives them to her.

SO:
Influenced by her desire to add to the story of Sophie and Albert, Hilde subconsciously unties the boat and lets it drift in the same style as Sophie while she is sitting on the dock waiting for the major to come home.

Comments? I would love to hear them.

Alright, I'm going to join you in being impressed with the ending. However, I was pretty darn confused about the scientific probability of the events in the conclusion.
I like your idea of Hilde having created a new beginning for Sophie and Albert, sort of as if her interest overcame the Major's creation. Like he subconsciously passed it on to his daughter.
Also, Freud's idea of the icebergs.. it could be like Hilde's iceberg shifted closer to theirs, and she pushed the Major's out of the way.
Good ideas. :)