Chapter

Logical Necessity

Ian Rumfitt

in The Boundary Stones of Thought

Published in print March 2015 | ISBN: 9780198733638
Published online June 2015 | e-ISBN: 9780191798016 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780198733638.003.0003
Logical Necessity

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Aristotle discerned a modal element in the notion of consequence: if a conclusion follows from some premisses, it is necessary that the conclusion is true whenever all the premisses are true. This chapter develops the account of consequence relations from Chapter 2 to provide a new argument for Aristotle’s thesis. It is further argued that a particular modality of logical necessity is implicit in the notion of specifically logical consequence. The chapter then investigates the relationships that obtain between logical necessity and other forms of necessity (notably metaphysical necessity), and between logical necessity and apriority. This investigation culminates in a qualified defence of Ian McFetridge’s claim that logical necessity is the strongest form of non-epistemic necessity against the objections of Dorothy Edgington.

Keywords: logical consequence; logical necessity; metaphysical necessity; apriority; Lindenbaum-Scott Theorem; modal logic S5; Dana Scott; Ian McFetridge; Dorothy Edgington

Chapter.  13181 words. 

Subjects: Philosophy of Mind

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