Formal Ontology, Propositional Identity and Truth Conditions With an Application of the Theory of Types to the Logic of Modal and Temporal Propositions

In the philosophical tradition, propositions have a double nature. On one hand, they are units of sense of a fundamental logical type. They are senses of sentences provided with truth conditions. Each proposition is true in a circumstance when it represents a fact which exists in that circumstance. So any analysis of the logical form of propositions requires a theory of truth. On the other hand, propositions are also the contents of conceptual thoughts that we, human beings, have whenever we represent facts of the world. In particular, they are the contents of illocutionary acts like assertions, promises and questions that we perform in the use of language. They are also the contents of our attitudes (beliefs, desires, intentions) towards objects and facts. As Frege pointed out, the two intrinsic aspects of propositions are logically related. For we cannot express a propositional content in thinking and speaking without relating it eo ipso to the world with a certain force. Any literal meaningful utterance of an elementary sentence is always an attempt by the speaker to perform an illocutionary act with a force F and a propositional content P. 3 So force, sense and denotation are the three basic components of sentence meaning in the logical structure of language. And the proposition which is the sense of an elementary sentence in a context of utterance is also the content of the elementary illocutionary act that the speaker of that context would mean to perform if he or she were using that single sentence literally. The main purpose of this chapter is to formulate a new theory of sense and denotation that takes into account the double nature of propositions. The fact that propositions are contents of conceptual thoughts imposes to propositional logic many conditions of material and formal adequacy that logicians have unfortunately tended to