This chapter focuses on the problem of the reference in perception, the problem of the role of action in reference-fixing, and the reference of the theoretical terms of scientific theories. Epistemological constructivism undermines realism by arguing that the experience of the world is mediated by the concepts, and that there is no direct way to examine which aspects of objects belong to them independently of the conceptualizations. Semantic constructivism attacks realism on the ground that there is no direct way to set up the relation between the terms of representations and the entities to which they purportedly refer. For realism to fight back, realists must undermine both epistemological and semantic constructivism. The task of the realist would be to examine the assumptions underlying these two theories of reference, and try to figure out a way to overcome their difficulties by revising or undermining the underlying assumptions.