 A final group of views in the literature represents a kind of agnosticism about what exists or about what it is to be an object, be it abstract or concrete. These views don’t reject an external material world, but rather begin with some question as to whether we can have experience, observation, and knowledge of objects directly, i.e., independent of our theoretical frameworks. Carnap (1950 [1956]), for example, started with the idea that our scientific knowledge has to be expressed with respect to a linguistic framework and that when we wish to put forward a theory about a new kind of entity, we must have a linguistic framework for talking about those entities. He then distinguished two kinds of existence questions: internal questions within the framework about the existence of the new entities and external questions about the reality of the framework itself. If the framework deals with abstract entities such as numbers, sets, propositions, etc., then the internal question can be answered by logical analysis of the rules of the language, such as whether it includes terms for, or implies claims that quantify over, abstract objects. But, for Carnap, the external question, about whether the abstract entities really exist, is a pseudo-question and should be regarded as nothing more than the pragmatic question of whether the framework is a useful one to adopt, for scientific or other forms of enquiry. We’ll discuss Carnap’s view in more detail in  subsection 3.7.1.