The Dwellers held that the ability to suffer was what ultimately marked out sentient life from any other sort. They didn't mean just the ability to feel physical pain, they meant real suffering, they meant the sort of suffering that was all the worse because the creature undergoing the experience could appreciate it fully, could think back to when it had not suffered so, look forward to when it might stop (or despair of it ever stopping - despair was a large component of this) and know that if things had been different it might not be suffering now. Brains required, see? Imagination. Any brainless thing with a rudimentary nervous system could feel pain. Suffering took intelligence.
Banks, Iain (2004). "The Algebraist".
Qué bueno que se terminaron las clases y que mis papás han tenido que ir al dentista 2 días seguidos; estoy a 10 páginas del capítulo 4 :3 Sólo hice un break porque empezaban a mencionar al personaje que me cae gordo y me acordé de que ayer en el dentista leí este pedacito y se me hizo ohmygod so brilliant.