Quantum Mechanics and Objectivity: A Study of the Physical Philosophy of Werner Heisenberg

Quantum mechanics has raised in an acute form three problems which go to the heart of man's relationship with nature through experimental science: (r) the public objectivity of science, that is, its value as a universal science for all investigators; (2) the empirical objectivity of scientific objects, that is, man's ability to construct a precise or causal spatio-temporal model of microscopic systems; and finally (3), the formal objectivity of science, that is, its value as an expression of what nature is independently of its being an object of human knowledge. These are three aspects of what is generally called the "crisis of objec­ tivity" or the "crisis of realism" in modern physics. This crisis is. studied in the light of Werner Heisenberg's work. Heisenberg was one of the architects of quantum mechanics, and we have chosen his writings as the principal source-material for this study. Among physicists of the microscopic domain, no one except perhaps Bohr has expressed himself so abundantly and so profoundly on the philosophy of science as Heisenberg. His writings, both technical and non-technical, show an awareness of the mysterious element in scientific knowledge, far from the facile positivism of Bohr and others of his contemporaries. The mystery of human knowledge and human SUbjectivity is for him an abiding source of wonder.

I: Objectivity in Quantum Mechanics.- The Epistemological Structure of Quantum Mechanics.- One: Introduction.- I. Methodological Introduction: Intentionality and World — Objects and Objectivity — Subjectivity — Reality and its Criterion — The World of Modern Physics.- II. Philosophical Introduction: Introduction — Being and Truth — Concepts and Abstraction — Deterministic (Causal) Theories — Probabilistic Theories — Probability and Human Ignorance — Probability of Evidence — Summary.- Two: The Discovery of Quantum Mechanics.- I. Werner Heisenberg and Quantum Mechanics: Introduction — Quantum Mechanics.- II. Intentionality Structure of Classical Physics.- III. Crisis of the Classical Intentionality-Structure: Crisis — A Physics of “Observables”.- IV. Quantum Mechanics, a New Kind of Physical Theory: A Theory of Operators — Novelty of Quantum Mechanics.- V. Quantum Mechanics and Wave Mechanics, 1926: Wave Mechanics — Heisenberg and Schrödinger.- VI. The Indeterminacy Relations of 1927: The Intuitive Meaning of Quantum Mechanics — The Indeterminacy Relations.- VII. The Indeterminacy of the Factual: Enriching Abstraction — Ignorance and Nescience — The Relational Structure of Physical Variables — The Wave Packet — Summary.- Three: The Intentionality of Structure of Complementarity.- I. Bohr and Complementarity: The Copenhagen Spirit — Complementarity.- II. Heisenberg and Complementarity: Heisenberg and Complementarity — Wave-Particle Duality in Heisenberg — Causality in Heisenberg — Heisenberg’s View of Physics.- III. The Intentionality Structure of Complementarity — Summary.- Four: Complementarity and the Scientific Method A Criticism.- I. Proposition (1) on Scientific Method: Proposition (1) — Criticism — Psycho-physical Parallelism — A Pseudoproblem — Conclusion.- II. Proposition (2) on Scientific Method: Proposition (2) — General Criticism — The Relational Structure of Physical Properties — Remnants of Classical Rationalism — The Indeterminacy Relation.- III. The Quantum Theory of Measurement: Three Stages of a Measurement — Formation of a Mixture — Act of observation — The Observer in Quantum Mechanics — Reduction of the Wave Packet — Objectivity of Quantum Mechanics — Summary.- Five: Subjectivity and Objectivity.- I. Subjectivity and Objectivity Defined: Public Objectivity — Thing — Body — Empirical Objectivity — Formal Objectivity — Reality and its Criterion — Subjectivity.- II. Empirical Objectivity: Objectivity and Exteriority.- III. Public Objectivity: Heisenberg and Public Objectivity — The “Subjective Element” — Problem of Public Objectivity in Quantum Mechanics — The Private World of the Observer — Solution of the Problem — Wave Function.- IV. Formal Objectivity: Formal and Public Objectivity — Wave Particle Duality Re-interpreted — Various Unitary Re-interpretations — The Strict Object of Quantum Mechanics — Matter-Form — Summary.- Six: Classical Mechanics and Quantum Mechanics.- I. Quantum and Classical Analogues: Classical Analogue of Quantum Mechanics.- II. The Correspondence Principle: Various Uses.- III. Completeness of Quantum Mechanics: Completeness Principle — Summary.- II Reality in Quantum Mechanics.- The Ontological Structure of Atomic Systems.- Seven: Various Theories of Reality in Physics.- I. Introduction: Science and Ontology.- II. Rationalist Tendencies: Universality and Necessity — Einstein — Critique.- III. Empiricist Tendencies: Empiricism and Quantum Mechanics — Instrumentalism — Wigner — Critique — Summary.- Eight: Reality in Heisenberg’s Philosophy.- I. The Early Heisenberg: General Outline — Heisenberg’s Empiricism — Influence of Plato.- II. Heisenberg and Kant: The Crisis of Kantian Critique.- III. The Mature Heisenberg: Abgeschlossene Theorien — Universal Equation of Matter — Natural Symmetries — Objectivity — Aristotelian “Potentia”.- IV. Heisenberg’s “Practical Realism”: Heisenberg and Kant — Heisenberg and Plato — Heisenberg and Aristotle — Summary.- Nine: Ontological Structure of Physical Reality.- I. Justification of Realism in Physical Science: “Reality” and Human Polymorphic Consciousness-Heisenberg’s Ontology Criticised — “Reality”: a Complex Notion — Sensibility Conceptual Understanding — Rational Affirmation.- II. Ontological Structure of Atomic Reality: Whole and Part of an Atomic System — Energy: a “Universal Matter”? — The “Energy Ladder” — Irreducible Matter — Summary.- III The Structure of Physical Science.- Ten: Logic and Language of Science.- I. The Nature of a Physical Science: The Mathematicisation of Physics — Space and Time — The Primacy of the Instrument.- II. The Language of Physics: Two Languages — Summary.- Appendix: Law of Superposition of Wave Functions — Entropy and Information.- Glossary of Philosophical and Scientific Terms.