 Later, in his essay “The Thought” (1918), Frege claims the same status for the items he calls thoughts—the senses of declarative sentences—and also, by implication, for their constituents, the senses of subsentential expressions. Frege does not say that senses are abstract. He says that they belong to a third realm distinct both from the sensible external world and from the internal world of consciousness. Similar claims had been made by Bolzano (1837), and later by Brentano (1874) and his pupils, including Meinong and Husserl. The common theme in these developments is the felt need in semantics and psychology, as well as in mathematics, for a class of objective (i.e., non-mental) non-physical entities. As this new realism was absorbed into English-speaking philosophy, the traditional term ‘abstract’ was enlisted to apply to the denizens of this third realm. In this vein, Popper (1968) spoke of the ‘third world’ of abstract, objective entities, in the broader sense that includes cultural products such as arguments, theories, and works of art.