The wiksocion articles examples are bit inaccurate. I tried to find better source, but couldn't find right now. But the negativists think in negatives, in their thinking they eliminate what isn't/they don't like etc.. While positivists think the opposite way.
It's basically said in this part though: Positivists focus on the presence of something, whereas negativists focus primarily on the absence of something.
So a serious negativist would start an elimination process. But now I think I know what you were aiming at, you shouldn't remove what's uncertain, you can only remove what's certainly not.