ABSTRACT
The existential presumptions of a scientific language function as shared existential presuppositions underlying numerous core sentences of the language. An existential sentence, such as presupposes the existence of the denotation of the subject of the sentence. The term 'universal principles' is used by P. Feyerabend in his mature explication of the concept of incommensurability. Initially, Feyerabend calls universal principles 'fundamental rules or laws'. A presupposition of a sentence is a factual assumption about the existential state of the world around a language community. This means that as far as the function of truth-value status determination is concerned, a mode of reasoning should be conceived as the premises of reasoning, instead of as the form of reasoning. Historically, the universal principles of a cosmology were some explicit factual beliefs about the existential state of the world observed by a cultural or scientific tradition. A tradition is best characterized by the specific way of understanding the world.
