Also who can forget Nancy Kress' novela "Beggars in Spain" which address the question of what those of us in society who are productive owe those who are not (the beggars in spain question).
I guess this is a short fiction list, but i have to say, Terry Pratchett (would not be sci-fi, but fantasy I guess) explores lots and lots of philosophical questions and is well known for exploring human nature and the nature of evil.
In the sci-fi section, the book "The Gumshoe, the Witch, and the Virtual Corpse" explores the nature of religious identity and religious conflict in America. In particular, it explores religious tolerance and what precursors are necessary for religious tolerance in a democratic society.
In the sci-fi section, the book "The Gumshoe, the Witch, and the Virtual Corpse" explores the nature of religious identity and religious conflict in America. In particular, it explores religious tolerance and what precursors are necessary for religious tolerance in a democratic society.