In his article [S. T. Pai, Phys. Essays 28 , 55 (2015)], Pai indicates that the photon is both massive and massless. The claim of massless particles is based on the theory of special relativity. Particles distributed in empty space form the world. All particles have two properties independent of each other: mass and energy. There are no particles with no masses, and there are no particles with no energy. Mass cannot convert to energy, and energy cannot convert to mass. Particles that go from stillness to motion or from motion to stillness absorb or emit miniparticles, resulting in changes in their mass and energy. All particles in the world are massive.