"It's as if…" The man paused, seeming to search his mind for the right words of description. "It's like going downhill through deep snow on a sled," he said, finally. "At first it's exhilarating: the speed; the sharp, clear air; but then the snow accumulates, builds up on the runners, and you slow, you have to push hard to keep going and –" (10.59)
The Giver's metaphor is interesting. Memories are "exhilarating" at first because they're fun—think birthday parties and Christmas morning. But you have to remember that, in The Giver, happiness and suffering go hand in hand. You can't have one without the other. So after the good stuff comes the bad: warfare, pain, injury, isolation. This slows you down, hence the snow building up on the runners. If you want to read all about the significance of the sled in The Giver, check out Symbols, Imagery, and Allegory.
"There's much more. There's all that goes beyond – all that is Elsewhere – and all that goes back, and back, and back. I received all of those, when I was selected. And here in this room, all alone, I re-experience them again and again. It is how wisdom comes. And how we shape our future." (10.56)
If the wisdom of the past is necessary to make decisions of the future, then we can see why the community is so resistant to change. They don't have the knowledge they need to make choices, so everything stays the same.
He rested for a moment, breathing deeply. "I am so weighted with them," he said. (10.57)
Memories may bring wisdom, but they also bring pain. The Giverforces us to ask if it's worth the suffering to gain the knowledge.
"It hurt a lot," Jonas said, "but I'm glad you gave it to me. It was interesting. And now I understand better. What it meant, that there would be pain." (11.60)
Notice that, at first, Jonas is guilty of the same hollow use of language that he will later accuse his sister and mother of. He claims to "know" what "pain" "means," three words that will radically change in his mind as he gains more and more wisdom from the memories.
"But why can't everyone have the memories? I think it would seem a little easier if the memories were shared. You and I wouldn't have to bear so much by ourselves, if everyone took a part."
The Giver sighed, "You're right," he said, "But then everyone would be burdened and pained. They don't want that. And that's the real reason The Receiver is so vital to them, and so honored. They selected me – and you – to lift that burden from themselves." (14.46-47)
When you look at it this way, the community is guilty of cowardice. And, as we see, the price for this sort of action is high: they may escape pain, but they are deprived of wisdom as well.
"Rosemary had only those five weeks worth, and most of them were good ones. But there were those few terrible memories, the ones that overwhelmed her. For awhile they overwhelmed the community. All those feelings! They'd never experienced that before. (18.52)
When we read this, we can't help but wonder—as does Jonas—what would happen to the community were they to suddenly receive all the memories that Jonas has stored up. The Giver would seem to take a positive stance here; check out the end of the novel, where Jonas thinks he hears music coming from behind him. Sure, the community may be slapped across the face with the knowledge of all human suffering that has ever occurred in the world, but they also get music (and Christmas, and colors, and lights, and sunshine, and snow, etc., etc).