The entire topic is something I can't possibly wrap my mind around.

Actually, I can - sort of. My father was a holocaust survivor and a very traditional Jewish man born in Poland and descended from a line of Rabbis. During the war, he was captured in the woods and sent to Auschwitz where he spent 9 months until the Russians got too close. Then he was transferred to Dachau, where he spent another 9 months until he was liberated. When I asked him how he could survive the atrocities, he told me that he thought that he was a young man (he was in his early 20's) and he believed that one day the war would be over and he would have his whole life ahead of him. Well, the joke was on him. He came to the United States where he met and married my mother, who made him miserable for the rest of his life. Being an old school Jew, divorce was just not an option for him. So the only escape in his mind was suicide.

I gave the eulogy at his funeral, and this line from Henry David Thoreau's "Civil Disobedience" seemed to me to sum up my father's life:

“Most men lead lives of quiet desperation and go to the grave with the song still in them.”

It was the line that began his eulogy.

In his letter, he told me that a year prior, he was so down on his prospects that he would have wound up dead. To this day, I don't know if I'm more happy I was able to help him, or more disturbed that he would have done it had things not turned out well for him.

Hmmm. I understand your sentiment but, ultimately, we are all responsible for our own actions. In my mind, suicide is a permanent solution to a temporary problem and it is the coward's way out.

Sometimes people are just plain incomprehensible.

Just sometimes? There are times that I can't understand myself, so I don't expect to understand other people all that well. I think that the point is that, no matter how many friends and loved ones we have in our lives, ultimately we are all lonely, just by virtue of the fact that we are separated from the rest of humanity by our own skins. There is no way for you to crawl into someone else's mind and see things the way they do.