Generalization of Einstein's Principle of Equivalence so as to Embrace the Field Equations of Gravitation

It is shown that the apparent impossibility of deriving Einstein's field equations of gravitation in a way similar to that used by him in deriving the equations of particle motion and electromagnetism–being a direct generalization of his famous imaginary experiment of a box falling freely in a gravitational field–may be overcome by using the quantal vacuum with its fluctuations instead of the vacuum of ordinary physics with its absolute emptiness. Thus, the Dirac equation with gravitation, thereby used, appears, in contrast to the ordinary view, as the prototype of interaction theory based on general principles, one of them being a generalized principle of equivalence.