Abstract

History of modal logic begins with Aristotle who devoted two chapters of On Interpretation to a study of logical connections between the necessary, the impossible, the possible, and the permitted. In the Prior Analytics Aristotle discusses modal syllogisms i.e. syllogisms with modalized premises and conclusion. In On Interpretation he argues that every single assertion, such as premise or conclusion in a syllogism, is either an affirmation or a denial of a single predicate of a single subject; according to Aristotle, modal terms modify a given assertion or denial. The Megarians and Stoics developed various theories concerning modality, mostly in connection with propositional logic. According to them, modal terms modify propositions. Contemporary discussion of formal properties of modal terms begins with the work of C.I. Lewis Symbolic Logic and its Applications . Contemporary semantic analysis of modal terms, known as possible worlds semantics, initiated by S. Kripke , follows Leibniz suggestion that a sentence is necessarily true in this world if and only if that sentence is true in all worlds alternative to this world. The paper addresses several problems concerning the concepts of existence and possibility. Its aim is to show that contemporary analysis can capture some intuitions of Aristotle and his scholastic followers, especially those concerning the modalities de re. Key words LOGICAL ANALYSIS, EXISTENCE, NECESSITY.