The Schopenhauer Cure

In the novel, which is the subject of this post, why didn't Philip kill himself? I can't understand why he would choose to life a life that offered nothing but suffering.

Because he wasn't man enough to do it.

Not sure if you're trolling but I don't think that was the reason. The topic of suicide never ever came up in the book, I don't really understand why. Philip's most logical path was suicide but he didn't take it.

optimism? I don't know, haven't read the book