 The twosome denied by the denial of “duality” has many interpretations across Yogācāra thought, but for Vasubandhu the most important kinds of duality are conceptual duality and perceptual  duality.[42]  Conceptual duality is the bifurcation of the universe that appears necessary in the formation of any concept. When we say of any given thing that it is “physical,” we are effectively saying, at the same time, that all things are either “physical” or “not physical.” We create a “duality” according to which we may understand all things as falling into either one or the other category. This is what it is to define something, and to ascribe it its characteristic nature (svabhāva). This is why every “self” is “dual.” To say something is what it is imposes a duality upon the world. And, given that the world is in causal flux and does not accord with any conceptual construct, every duality imposes a false construct upon the world. To illuminate this with regard to the person, when I say that “I” exist, I am dividing the universe into “self” and “other”—me and not-me. Since, for Buddhists, the self is unreal, this is a mistaken imposition, and of course many ignorant, selfish actions follow from this fundamental conceptual error.