 Explanations of purported “conversions” along the lines suggested by Bondi and Spurgin are now commonplace in the physics literature. These explanations have the merit of emphasizing that in many cases the mysteries of mass-energy equivalence do not concern one physical property magically being transfigured into another. However, the Bondi-Spurgin interpretation of mass-energy equivalence has the demerit that it fails to address reactions such as the electron-positron annihilation reaction. In such reactions, not only is the number of particles not conserved, but all of the particles involved are, by hypothesis, indivisible wholes. Thus, the energy liberated in such reactions cannot be explained as resulting from a transformation of the energy that was originally possessed by the constituents of the reacting particles. Of course, Bondi and Spurgin may simply be hoping that physics will reveal that particles such as electrons and positrons are not indivisible wholes after all. Indeed, they may even use annihilation reactions combined with their interpretation of mass-energy equivalence to argue that it cannot be the case that such particles are indivisible. Thus, we witness here explicitly just how closely related interpretations concerning mass-energy equivalence can be to views concerning the nature of matter.