1. Metaphysics of Mass
Benjamin hayworth

2. Historical Context Medieval Conception Newtonian Conception
Inertial Mass
Gravitational Mass
Relativistic Mass
Mass-Energy Equivalence
Mass in General Relativity

3. Problems and Definitions
Point of View discrepancy
Observer Dependent
Definition Distinction
‘Mass’
‘mass’

4. Possible Criterion of Identity
1. Armstrong – Causally Significant and Instantiated
2. Lange – Lorentz Invariant
3. Why not both?

5. Mass-Energy Problem and Interpretations
1. Same Property – Eddington and Toretti
2. Different Properties without Conversion – Bondi and Spurgin
3. Different Properties with Conversion – Rindler
4. One Property – Lange

6. Flores’ Requirements
1. The interpretation of the theory should tell us what the world is like if the theory is true.
2. The interpretation does not appeal to any hypotheses outside of the theory.
3. The interpretation of the theory must be philosophically uniform.

7. 1. Same Property
Misconception that we view them as separate properties (much like Space and Time)
Talking about ‘Mass’ which we determined was not the real property (Lange)
Fails Requirement 2 (exotic forms of matter do not exist that wouldn’t convert to energy)

8. 2. Different Properties no Conversion
Energy HAS Mass
Necessary for all microscopic particles to be distinguished into further composite parts (no metaphysical atoms)
Fails Requirement 2 for reason above
Unless energy has ‘mass’ , they are treating mass as a first-order and second-order property.

9. 3. Different Properties with Conversion
Same as Interpretation 2, but allows for their to be true conversions from mass to energy (as in particle-antiparticle annihilation)
Flores chooses as the correct interpretation.
Same critiques I raised about Interpretation 2, as well as Lange’s critique of real property to unreal property.

10. 4. One Property Lange’s Lorentz Invariant Criterion
Space-Time Intervals
E.M. Waves
All a problem of perspective (mass=real, energy=unreal), so no conversion is possible as one is not an actual property of the object.
Fails Requirement 3 (faulty reason).

11. Properties Affected By Lange’s Criterion
Real:
‘mass’
Charge
Unreal:
‘Mass’
Length
Energy
Velocity
Force
Etc.

12. Solution Weaken Lange’s Criterion Original:
’p’ is a real property iff it is Lorentz Invariant
Weakened:
’p’ is an intrinsic property iff it is Lorentz Invariant