A Study On Deontic Logics And Deontic Paradoxes

Modern Deontic logic which originates from1950s-1960s is a kind of modal logic involving modal words like "obligation","permission", and other related expressions. Denontic logic, although considered as a new branch of modern logic, can be traced back to early times. At the time of Aristotles, logicians have been concerned with denotic modals.Logicians are very interested in modern deontic logic from the beginning. Based on von Wright’s classical denotic logic system, a lot of new denotic logical systems are constructed. Since1950s, deontic logics have been keeping steps with the development of modern formal logic. At the same time, Logicans overcome many difficulties in constructing deontic formal system, and attempt to resolve so-called paradoxes in these systems. With so many logicians’endeavors, today’s deontic logics have become an important part of general modal logics.This thesis aims at analyzing and studying the origin and development of deontic logics comprehensively, systematically and deeply. It also tries to give a detailed introduction to the background of deontic logic, the development of pioneer logician von Wright’s thoughts form unitary deontic logic to binary deontic logic, and the trend of modern deontic logic. Furthermore, it pays more attention to deontic paradoxes lying in systems of deontic logics. After analyzing many solutions to these deontic paradoxes and their difficulties, the author proposes an unary operator theory to solve deontic paradoxes.This thesis also gives a concise appreciation of the solutions to three famous deontic paradoxes in order that we can to some extent deepen our understanding to modern deontic logics. The development of deontic will only enrich content of philosophical logics, but also is helpful for broadening the fields of logics.