1 Probability, Pseudoprobability, Mean Values.- 1. Introduction.- 2. Pairs of Operators.- 3. Wigner's Pseudodensity.- 4. Probability Spaces.- 5. Quantum Mechanics and Fluid Dynamics.- 6. Marcinkiewicz Space and Stationary Functions.- 7. Conclusion.- 2 Local Vacua.- 1. From Bell's Theorem to Where?.- 2. Some Basic Facts about Nonlocality.- 3. How to Get Rid of the Wave Function Collapse.- 4. The Physical Nature of the Local Vacuum.- 5. Dirac's Covariant Vacuum as an Example.- 6. Conclusion and Outlook.- 3 Causal Quantum Theory: Why a Nonstarter?.- 1. Introduction.- 2. Formalism and Interpretation: An Example.- 3. The "Copenhagen" Interpretation.- 4. A Logically Possible, Empirically Viable Alternative: Causal Interpretations.- 5. A Modern "Double-Slit" Experiment.- 6. The Value of an Alternative Interpretation.- 7. Oposing Commitments, Opposing Schools.- 7.1. Cultural Milieux.- 7.2. The Wave-Mechanics Route.- 7.3. The Matrix-Mechanics Route.- 8. Forging the "Copenhagen" Interpretation.- 9. An Alternative Historical Scenario?.- 10. Internal versus External Explanations.- 4 Duality of Fluctuations, Fields, and More.- 1. Introduction.- 2. Duality of Fluctuations.- 2.1. Generalized Wave-Particle Fluctuations.- 2.2. Nonclassical States.- 3. Duality of Fields.- 3.1. Classical Fields.- 3.2. Nonclassical Fields.- 3.3. The Vacuum.- 4. Duality of the Radiation Process.- 4.1. Two Kinds of Radiation Processes.- 4.2. Spontaneous Emission.- 4.3. Stimulated Emission.- 4.4. Stimulation (of Induced Emission): The Blake-Scarl Experiment.- 4.5. Stimulation (of Spontaneous Emission).- 4.6. A Hypothesis.- 5. The Unobservable Wave.- 5.1. Empty Waves and Duality.- 5.2. Blake-Scarl.- 5.3. Selleri and Others.- 5.4. Mückenheim et al.- 5.5. Martinolli-Gozzini.- 5.6. Conclusion.- 6. Discussion: Measurement and Duality.- 6.1. Locality.- 6.2. Unitarity.- 6.3. Duality and Reality.- 5 Dualism within Dualism: Open Questions.- 6 Recent Contributions of Electron Interferometry to Wave-Particle Duality.- 1. Introduction.- 2. The Novel Electron-Optical Biprism Interferometer.- 3. Electron Interferometric Verifications of Wave-Particle Duality.- 3.1. Early Experiments: Diffraction at an Edge, Electron Biprism Interferences, and Diffraction by Slits.- 3.2. Novel Experiments.- 7 The Aharonov-Bohm Effect From the Point of View of Local Realism.- 1. Introduction.- 2. Theory of the AB Effect.- 3. Looking Beyond the Mathematical Formalism.- 4. Local Realist Interpretation of the AB Effect.- 8 Are Two-Beam Self-Interferences Mass-Independent? Not Thoroughly Known (?) Role of the Mass.- 1. Introduction and Historical Backgrounds.- 2. Propositions of New Test Experiments.- 2.1. Modified Neutron Double Slits.- 2.2. TSPL versus V Curve.- 2.3. Effect of Source Size.- 2.4. Modified Ion Biprism.- 3. Is the Dirac Assumption Approximate or Not?.- 4. Hypothetical Model: The In-flight Transition before Arrival at Detector.- 5. Theoretical Perspectives.- 5.1. Irreversible Microscopic Process.- 5.2. Effect on EPR and Delayed Choice Experiments.- 5.3. Are Roles of the Mass "Not Thoroughly Known"?.- 6. Epistemological Remarks.- 9 Wave Mechanics and Relativity.- 1. Can We Reach Wave Mechanics Starting from Classical Mechanics?.- 2. Minimal Conditions of Wave-Particle Dualism: They Are Incompatible with Classical Mechanics and Require Relativity.- 3. A Note about a Reasoning of Hamilton.- 10 Unsharp Particle-Wave Duality in Double-Slit Experiments.- 1. Introduction.- 2. The Photon Split-Beam Experiment.- 3. The Unsharp Measuring Process.- 4. Information Theoretical Considerations.- 5. Realization of the Unsharp Joint Measurement of P(A) and P(B).- 6. Neutron Interference Experiments.- 11 Some Arguments against the Existence of de Broglie Waves.- 1. Distinguishing Schrödinger's from de Broglie's Waves.- 2. De Broglie's Initial Concept of de Broglie Waves.- 3. Discussion of Models.- 4. Conclusion.- 12 On the "Completeness" of Quantum Mechanics.- 1. Background.- 2. Covering Theories: An Ex