   However, by 1918, Russell’s attitude with regard to quantified propositions had changed. He no longer believed that the truth of a general proposition could be reduced simply to the facts or complexes making its instances true.  Russell argued that the truth of the general proposition “(x).R(x,  b)” could not consist entirely of the various atomic facts that a bears R to b, b bears R to b, c bears R to b, …. It also requires the truth that there are no other individuals besides a, b, c, etc., i.e., no other atomic facts of the relevant form. Hence, Russell concluded that there is a special category of facts he calls general facts that account for the truth of quantified propositions, although he admitted a certain amount of uncertainty as to their precise nature (PLA, 234–37). Likewise, Russell also posited existence facts, those facts corresponding to the truth of existentially quantified propositions, such as “(∃x)R(x, b)”. In the case of general and existence facts, Russell did not think it coherent to make distinctions between positive and negative facts. Indeed, a negative general fact could simply be described as an existence fact, and a negative existence fact could be described as a general fact. For example, the falsity of the general proposition “all birds fly” amounts to the fact that there exist birds that do not fly, and the falsity of the existential proposition “there are unicorns” amounts to the general fact that everything is not a unicorn. Obviously, however, the truth or falsity of a general or existence proposition is not wholly independent of its instances.