Although the debate about the true nature of the quantum behavior of atomic systems has never ceased, there are two periods during which it has been particularly intense: the years that saw the founding of quantum mechanics and, increasingly, these modern times. In 1954 Max Born, on accepting the Nobel Prize for his 'fundamental researches in quantum mechanics', recalled the depth of the disagreements that divided celebrated quantum theorists of those days into two camps: . . . when I say that physicists had accepted the way of thinking developed by us at that time, r am not quite correct: there are a few most noteworthy exceptions - namely, among those very workers who have contributed most to the building up of quantum theory. Planck himself belonged to the sceptics until his death. Einstein, de Broglie, and Schriidinger have not ceased to emphasize the unsatisfactory features of quantum mechanics . . . . This dramatic disagreement centered around some of the most funda­ mental questions in all of science: Do atomic objects exist il1dependently of human observations and, if so, is it possible for man to understand correctly their behavior? By and large, it can be said that the Copenhagen and Gottingen schools - led by Bohr, Heisenberg, and Born, in particula- gave more or less openly pessimistic answers to these questions.

Inhalt

1 / Quantum Theorists and the Physical World.- 1.1. Three Central Questions about Physics.- 1.2. The Older Generation.- 1.3. The Middle Generation.- 1.4. The Younger Generation.- 1.5. Conclusions.- 2 / Is Quantum Mechanics a Complete Theory?.- 2.1. The Problem of Completeness and of Hidden Variables.- 2.2. De Broglie's Paradox.- 2.3. The Spin-1/2 System in Quantum Mechanics.- 2.4. A Simple Proof of von Neumann's Theorem.- 2.5. The Theorem is not General Enough.- 2.6. Von Neumann's Theorem: Assumptions, Definitions, and Results.- 2.7. General Proof of von Neumann's Theorem.- 2.8. Jauch and Piron's Theorem.- 2.9. The Debate on Impossibility Proofs.- 3 / The Wave-Particle Duality.- 3.1. Duality for Photons.- 3.2. Duality for Neutrons.- 3.3. Einstein's Discovery of Duality.- 3.4. De Broglie's Duality.- 3.5. Schrödinger's Waves.- 3.6. Bohr's Complementarity.- 3.7. Fock's Relativity with Respect to the Means of Observation.- 3.8. Heisenberg Beyond Complementarity.- 3.9. The Consciousness Interpretation.- 3.10. Delayed Choices.- 3.11. How to do what Complementarity Forbids.- 4 / Properties of Quantum Waves.- 4.1. Quantum Waves and Quantum Potential.- 4.2. Experiments on the Nature of Duality.- 4.3. Stimulated Emission.- 4.4. Quantitative Empty Wave Amplification.- 4.5. Two Further Experimental Proposals.- 4.6. Triple-Slit Experiments.- 4.7. The Bohm-Aharonov Effect.- 4.8. Further Ideas about Wave-Particle Duality.- 5 / The Einstein-Podolsky-Rosen Paradox.- 5.1. The Original Formulation.- 5.2. Bohr's Answer.- 5.3. Two Types of State Vectors.- 5.4. Spin States for Two Particles.- 5.5. Reality and Separability.- 5.6. The EPR Paradox: Quantum Mechanics Complete.- 5.7. The EPR Paradox: Quantum Mechanics not Complete.- 5.8. From Theory to Practice.- 5.9. The Experimental Information.- 5.10. Solution 1: Modifying the Past.- 5.11. Solution 2: Superluminal Connections.- 5.12. Solution 3: New Definitions of Probability.- 5.13. Solution 4: Modifications of Quantum Theory.- 6 / The EPR Paradox in the Real World.- 6.1. Criticisms of Einstein Locality.- 6.2. Probabilistic Einstein Locality.- 6.3. New Proof of Bell's Inequality.- 6.4. Probabilities for Pairs of Correlated Systems.- 6.5. A New Factorizability Condition.- 6.6. All the Inequalities of Einstein Locality.- 6.7. Tests of the EPR Paradox in Particle Physics.- 6.8. On the Possibility of New Experiments.- 6.9. Variable Probabilities.- 7 / Perspectives of Physical Realism.- 7.1. Objectivity of Scientific Knowledge.- 7.2. Mathematics and Reality.- 7.3. The Role of History of Physics.- 7.4. Fragmentation of Modern Physics.- 7.5. Niels Bohr and Philosophy.- 7.6. Quantum Physics and Biological Sciences.- 7.7. Forms of Physical Realism.