1. Introduction – Craig Callender and Nick Huggett
1.1. Why Quantum Gravity?
1.2. Must the Gravitational Field Be Quantized?
1.3. Approaches to Quantum Gravity
1.4. What Quantum Gravity and Philosophy Have to say to Each Other
Part one: Theories of Quantum Gravity
2. Spacetime and the Philosophical Challenge of Quantum Gravity – Jeremy Butterfield and Christopher Isham
2.1. Introduction
2.2. Conceptual Problems of Quantum Theory and General Relativity
2.3. Introducing Quantum Gravity
2.4. Research Programmes in Quantum Gravity
2.5. Towards Quantum Spacetime?
3. Naive Quantum Gravity – Steven Weinstein
3.1. Introduction
3.2. What is a field?
3.3. The uncertainty of quantization
3.4. Quantifying the effects of gravity–-local field strength
3.5. Causal structure
3.6. What's the point?
3.7. Conclusion
4. Quantum Spacetime: What Do We Know? – Carlo Rovelli
4.1. The Incomplete Revolution
4.2. The Problem
4.3. Quantum Spacetime
4.4. Considerations on Method and Content
Part two: Strings
5. Reflections On The Fate Of Spacetime – Edward Witten
5.1. Introduction
5.2. String Theory
5.3. Some Of The Symptoms
5.4. Duality and the Minimum Length
5.5. Strings and Quantum Mechanics
6. A Philosopher Looks at String Theory – Robert Weingard
7. Black Holes, Dumb Holes, and Entropy – William Unruh
7.1. Thermodynamics of Black Holes
7.2. A Problem in the Derivation of Black Hole Evaporation
7.3. Dumb Holes
7.4. Entropy and the `Information Paradox'
7.5. Conclusion
Part three: Topological Quantum Field Theory
8. Higher-Dimensional Algebra and Planck Scale Physics – John Baez
8.1. Introduction
8.2. The Planck Length
8.3. Topological Quantum Field Theory
8.4. 3-Dimensional Quantum Gravity
8.5. Higher-Dimensional Algebra
8.6. 4-Dimensional Quantum Gravity
Part four: Quantum Gravity and General Relativity
9. On General Covariance and Best Matching – Julian Barbour
9.1. Introduction
9.2. Einstein's Understanding of General Covariance
9.3. General Covariance Is Not a Physical Principle
9.4. Penrose's Argument
9.5. The Significant Issue
9.6. Conclusions
10. Pre-Socratic Quantum Gravity – Gordon Belot and John Earman
10.1. Introduction
10.2. Hamiltonian and Gauge Systems
10.3. General Relativity as a Gauge Theory
10.4. Gauge Invariance and Change
10.5. Life Without Change
10.6. Vive le Change!
10.7. The Status of Spacetime
11. The Origin of the Spacetime Metric: Bell's `Lorentzian Pedagogy' and its Significance in General Relativity – Harvey Brown and Oliver Pooley
11.1. Introduction
11.2. Chalk and cheese: Einstein on the status of special relativity theory
11.3. The significance of the Lorentzian pedagogy
11.4. Einstein's unease about rods and clocks in special relativity
11.5. A digression on rods and clocks in Weyl's 1918 unified field theory
11.6. The case of general relativity
Part five: Quantum Gravity and Quantum Mechanics
12. Quantum Spacetime Without Observers – Sheldon Goldstein and Stefan Teufel
12.1. Introduction
12.2. The conceptual problems of quantum gravity
12.3. The basic problem of orthodox quantum theory: the lack of a coherent ontology
12.4. Bohmian mechanics
12.5. Bohmian quantum gravity
12.6. A universal Bohmian theory
13. On Gravity's Role in Quantum State Reduction – Roger Penrose
13.1. The Problem of Quantum State Reduction
13.2. Stationary States
13.3. Preliminary Considerations
13.4. Superposed Gravitational Fields
13.5. The Semiclassical Approach
13.6. Approximate Space-time Point Identification
13.7. Further Considerations
14. Why the Quantum Must Yield to Gravity – Joy Christian
14.1. Introduction – From Schrodinger's Cat to Penrose's `OR'
14.2. How Spatio-temporal Events Lost Their Individuality
14.3. Penrose's Mechanism for the Objective State Reduction
14.4. A Closer Look at Penrose's Proposal within Newton-Cartan Framework
14.5. Concluding Remarks