A textbook on modal logic, intended for readers already acquainted with the elements of formal logic, containing nearly 500 exercises. Brian F. Chellas provides a systematic introduction to the principal ideas and results in contemporary treatments of modality, including theorems on completeness and decidability. Illustrative chapters focus on deontic logic and conditionality. Modality is a rapidly expanding branch of logic, and familiarity with the subject is now regarded as a necessary part of every philosopher's technical equipment. Chellas here offers an (...) up-to-date and reliable guide essential for the student. (shrink)

_Naming and Necessity_ has had a great and increasing influence. It redirected philosophical attention to neglected questions of natural and metaphysical necessity and to the connections between these and theories of naming, and of identity. This seminal work, to which today's thriving essentialist metaphysics largely owes its impetus, is here reissued in a newly corrected form with a new preface by the author. If there is such a thing as essential reading in metaphysics, or in philosophy of language, this is (...) it. (shrink)

Modal propositional logic; Modal predicate logic; A survey of modal logic.

Normal propositional modal systems This first chapter has two main aims. One is to give a general account of the propositional modal systems that we shall ...

In the first section of this paper I offer a necessary condition for members of a particular class of arguments to be acceptable asproofs. In the second section, I point out that a plausible extension of this principle reveals that a number of additional arguments cannot function successfully as proofs. Finally, I note that a number of theological arguments, particularly cosmological and ontological arguments, are suspect in the light of this extended principle. Standardly in the ontological argument, criticism falls on (...) the conditional, modality-enriching premise which involves a move from possibility to actuality. I offer two defences of this premise, and argue that—as the use of Moore's extended maxim shows—the problem lies with the premise that asserts mere possibility. (shrink)

There are five main claims that may be made about life after death: We are reincarnated in the self-same body we had in life. We are reincarnated in another body. We are revived, or continue to live in a disembodied form.

Lemmon and Scott introduced the notion of a modal system's providing the rule of disjunction. No consistent normal extension of KB provides this rule. An alternative rule is defined, which KDB, KTB, and other systems are shown to provide, while K and other systems provide the Lemmon-Scott rule but not the alternative rule. If S provides the alternative rule then either —A is a theorem of S or A is whenever A -> ΠA is a theorem; the converse fails. It (...) is suggested that systems with this property are appropriate for handling sorites paradoxes, where D is read as 'clearly*. The S4 axiom fails in such systems. (shrink)

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