 For Mach the world presents itself as “a viscous mass [of elements], at certain places (as in the ego) more firmly coherent than in others” (Mach 1886: 17). The neutral elements (only a minute fraction of which are sensations) and their relations are the basic reality. We draw boundaries around certain groups of elements that are related to each other in interesting ways, because this serves our purposes—the purposes of science and of ordinary life. We can continue to talk about material things and selves; it is economical to do so. But, strictly speaking, “both [object and ego] are provisional fictions of the same kind” (Mach 1905: 9).