A white hole is one possible solution to the Einstein field equations, as is a black hole. Mathematical possibilities, however, are not always realized in nature. We already have reason to believe GR is an incomplete description of gravity, and will remain so until we have a valid theory of quantum gravity - which is a possibility in the not so distant future. Once we unify quantum physics with GR many puzzles with things like black holes and white holes should be resolved. In the mean time we must rely on observational evidence to realize the distinction between reality and mathematical artifacts. The observational evidence favoring black holes as a valid solution to EFE is overwhelming. The evidence favoring white holes is virtually nonexistent. The prime directive in physics is a theory is nothing more than a hypothesis until until predictions made by that theory are confirmed by observational evidence.