There are significant problems involved in determining the ontology of quantum field theory. An ontology involving particles seems to be ruled out due to the problem of defining localized position operators, issues involving interactions in QFT, and, perhaps, the appearance of unitarily inequivalent representations. While this might imply that fields are the most natural ontology for QFT, the wavefunctional interpretation of QFT has significant drawbacks. A modified field ontology is examined where determinables are assigned to open bounded regions of spacetime (...) instead of spacetime points. (shrink)

Some physicists and philosophers argue that unitarily inequivalent representations in quantum field theory are mathematical surplus structure. Support for that view, sometimes called ‘algebraic imperialism’, relies on Fell’s theorem and its deployment in the algebraic approach to QFT. The algebraic imperialist uses Fell’s theorem to argue that UIRs are ‘physically equivalent’ to each other. The mathematical, conceptual, and dynamical aspects of Fell’s theorem will be examined. Its use as a criterion for physical equivalence is examined in detail and it is (...) proven that Fell’s theorem does not apply to the vast number of representations used in the algebraic approach. UIRs are not another case of theoretical underdetermination, because they make different predictions about ‘classical’ operators. These results are applied to the Unruh effect where there is a continuum of UIRs to which Fell’s theorem does not apply. _1_ Introduction _2_ Weak Equivalence and Physical Equivalence _3_ Mathematical Overview of Algebraic Quantum Field Theory _4_ Fell’s Theorem and Philosophical Responses to Weak Equivalence _5_ Weak Equivalence in C*-Algebras and W*-Algebras _6_ Classical Equivalence and Weak Equivalence _7_ Interlude: Is Weak Equivalence Really Physical Equivalence? _8_ The Unruh Effect _9_ Time Evolution and Symmetries _10_ Conclusions Appendix. (shrink)

The conserved quantities theory of causation (CQTC) attempts to use physics as the basis for an account of causation. However, a closer examination of the physics involved in CQTC reveals several critical failures. Some of the conserved quantities in physics cannot be used to distinguish causal interactions. Other conserved quantities cannot always be the properties of fields or particles. Finally, CQCT does not account for causal interactions that are static.

Philosophy of Logic: 5 Questions is a collection of interviews with some of the world's most influential and prominent scholars working on philosophy of logic. The questions: Why were you initially drawn to the philosophy of logic? What are your main contributions to the philosophy of logic? What is the proper role of philosophy of logic in relation to other disciplines, and to other branches of philosophy? What have been the most significant advances in the philosophy of logic? What are (...) the most important open problems in philosophy of logic, and what are the prospects for progress? Interviews with JC Beall, John Lane Bell, Johan van Benthem, Patricia A. Blanchette, OtAvio Bueno, James Cargile, Mark Colyvan, Newton Carneiro Affonso da Costa, Pascal Engel, Susan Haack, Jaakko J. Hintikka, Dale Jacquette, Penelope Maddy, Lawrence S. Moss, Catarina Dutilh Novaes, Ahti-Veikko Pietarinen, Graham Priest, Stephen Read, Nicholas Rescher, Stewart Shapiro, Peter Simons, Timothy Williamson, Jan Wole ski ". (shrink)

It is usually assumed that the modal ontological argument is valid. However, the logical system in which the argument is analyzed can require different assumptions to secure validity. Some strategies for the both critics and proponents of the modal ontological argument are examined in different logical systems. For agnostics, statements involving a perfect being may have a truth value other than true or false. A many-valued modal logic may be a more suitable framework for agnostics, and the modal ontological argument (...) will be invalid in some many-valued modal logics. These considerations show that defenders of the modal ontological argument must also defend the choice of a particular logic (or class of logics) as the appropriate setting where the argument should be evaluated. (shrink)

It is usually assumed that the modal ontological argument is valid. However, the logical system in which the argument is analyzed can require different assumptions to secure validity. Some strategies for the both critics and proponents of the modal ontological argument are examined in different logical systems. For agnostics, statements involving a perfect being may have a truth value other than true or false. A many-valued modal logic may be a more suitable framework for agnostics, and the modal ontological argument (...) will be invalid in some many-valued modal logics. These considerations show that defenders of the modal ontological argument must also defend the choice of a particular logic (or class of logics) as the appropriate setting where the argument should be evaluated. (shrink)