Absolute identity seems at first sight to be presupposed in the branch of formal logic called identity theory. Classical identity theory may be obtained by adjoining a single schema to ordinary quantification theory.

INTENSIONAL LOGIC §1. Natural Language and Intensional Logic When we speak of a theory of meaning for a natural language such as English, we have in mind an ...

Department of History and Philosophy of Science. University of Cambridge, Free School Lane, Cambridge CB2 3RH This paper is concerned with the question of whether atomic particles of the same species, i. e. with the same intrinsic state-independent properties of mass, spin, electric charge, etc, violate the Leibnizian Principle of the Identity of Indiscernibles, in the sense that, while there is more than one of them, their state-dependent properties may also all be the same. The answer depends on what exactly (...) the state-dependent properties of atomic particles are taken to be. On the plausible interpretation that these should comprise all monadic and relational properties that can be expressed in terms of physical magnitudes associated with self-adjoint operators that can be defined for the individual particles, then the weakest form of the Principle is shown to be violated for bosons, fermions and higher-order paraparticles, treated in first quantization *Some of the arguments inn this paper appeared in a thesis submited by one of us (S.F.) In partial fulfilment of the requirements for the PhD degree of the University of London, in 1984. entitled 'Identity and ‘Individuality in Classical and Quantum Physics’. (shrink)

It has been suggested that quantum particles are genuinelyvague objects (Lowe 1994a). The present work explores thissuggestion in terms of the various metaphysical packages that areavailable for describing such particles. The formal frameworksunderpinning such packages are outlined and issues of identityand reference are considered from this overall perspective. Indoing so we hope to illuminate the diverse ways in whichvagueness can arise in the quantum context.

Originally published in Italian in 1976, this book describes the methods scientists use to investigate the physical world. It is ideal for students and teachers of science and the philosophy of science. It is both a high-level popularization and a critical appraisal of these methods, describing important advances in physics and analyzing the historical development, value, reliability and philosophical implications of the way physicists approach the problems confronting them. The introductory chapter on the meaning of physical theories and the mathematical (...) tools used to develop them is followed by a general discussion on the foundations of physics under four major headings: the physics of the reversible, the physics of the irreversible, microphysics, and cosmology. Throughout, the subject matter of physical theories is linked to discussion of the attendant philosophical and epistemological implications, such as the validity of the theories, inductive inference, causal explanation, probability, the role of observation and the reality of physical objects. (shrink)