I read this a few days ago and was underwhelmed by the choices. If you're a writer and you have to find one word to sum up the foundation of what it is you do and, as such, who you are, it should be a colossal word. Lethem's furniture is good, but it seems a bit of a tongue-in-cheek response. Olivia Rosenthal chose No, which I think is super because fiction cannot exist if the characters just go along for the ride. Someone at some point as to say or act no. Nelly Arcan picked disappointment, which also seems like a good one, as it too can be motivation for all action--disappointment in one's self, one's environment, in fate.
But so many would work. Search. Desire. Uncertainty. There must be one overriding word that could take their place. I'll be figuring it out. Let me know if you find it.