I think that in *most* cases, to truely understand something, it must be experienced first-hand. It's possible, I think, to get close (maybe) to understanding something without having been there yourself (like through an analogy) but "being there" -- no matter how close you've been -- is completely different than simply trying to imagine it.
The personal example that comes to mind is the night I went from imagining what I would do if I were attacked by a stranger (like many women do) to actually being attacked. I reacted in so many different, conflicting (ultimately victorious
) ways, and the experience was *nothing* like what I had imagined in the past. After that experience, I had to look at how I thought of it previously so that I could understand how my friends, co-workers, and family responded to my story. It was strange, for sure.
Anyway, now I have a much different response when talking to someone who has been through the same or similar experience -- I can be more sympathetic rather than "well you should have done this" or "studies show that if you ..." -- all the funky crap that people come up with who haven't been through the same thing.
I think that it must be kind of the same in different experiences, as well -- like blind vs. seeing or married vs. divorced or a victim of a terrorist attack vs. the rest of us who weren't there. We can empathise, but we can't actually understand the experience unless we've been there.