The Multiverse Perspective on Determinateness in Set Theory
The multiverse view Ontology of Forcing Case Studies: CH, V = L Multiverse Axioms Multiverse Mathematics The multiverse perspective on determinateness in set theory Joel David Hamkins New York University, Philosophy The City University of New York, Mathematics College of Staten Island of CUNY The CUNY Graduate Center Exploring the Frontiers of Incompleteness Harvard University, October 19, 2011 The multiverse perspective, Harvard EFI 2011 Joel David Hamkins, New York The multiverse view Ontology of Forcing Case Studies: CH, V = L Multiverse Axioms Multiverse Mathematics Introduction Set theory as Ontological Foundation Set theorists commonly take their subject to serve as a foundation for the rest of mathematics, in the sense that other abstract mathematical objects can be construed fundamentally as sets, and in this way, they regard the set-theoretical universe as the realm of all mathematics. On this view, mathematical objects—such as functions, groups, real numbers, ordinals—are sets, and being precise in mathematics amounts to specifying an object in set theory. A slightly weakened position remains compatible with structuralism, where the set-theorist holds that sets provide objects fulfilling the desired structural roles of mathematical objects, which therefore can be viewed as sets. The multiverse perspective, Harvard EFI 2011 Joel David Hamkins, New York The multiverse view Ontology of Forcing Case Studies: CH, V = L Multiverse Axioms Multiverse Mathematics Introduction The Set-Theoretical Universe These sets accumulate transfinitely to form the universe of all sets. This cumulative universe is regarded by set theorists as the domain of all mathematics. The orthodox view among set theorists thereby exhibits a two-fold realist or Platonist nature: First, mathematical objects (can) exist as sets, and Second, these sets enjoy a real mathematical existence, accumulating to form the universe of all sets.
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