Objects and Pseudo-Objects: Ontological Deserts and Jungles from Brentano to Carnap

The development of science, logic, mathematics, and psychology in the 19th century made it necessary to introduce a growing number of new entities, of which classical empiricism and strong extensionalism were unable to give a wholly satisfying account. One of the major issues confronting the 20th century philosophers was to identify which of these entities should be rationally accepted as part of the furniture of the world and which should not, and to provide a general account of how the la...