You'd think you could just say "Dave's sad, his dog is dead, he wishes it were alive again, he's lonely" but you have to make all these stupid inferences and spread it out into five 8-sentence paragraphs. So I've read the lyrics about ten times now and I've been taking notes and trying as hard as possible to imagine every single one of Dave's emotions.
It's sad that I have to dig deep though. I don't like doing this with songs, I just like to sink into them and not have to care about logic and reason. But I think the dog in the trees means the dog's in heaven.
Ugghhh, I hope this project is over soon. Nice job, Mrs. See, assigning us a big paper when it's common knowledge that we're supposed to be studying our asses off for the standard finals :-/

I found some people discussing the same thing here. I do think the concept is pretty simple, but some people get pretty in to it. It is always fun to play with song meanings.

http://www.songmeanings.net/songs/view/3530822107858532017/

Hey, stranger!

Oh man, mental images causing me to chuckle in public. Stop doing this to me G.O.!