If God Made the Universe, then Who or What Made God?

If God made the universe, then who made God?

See University of Notre Dame philosopher Peter van Inwagen answer this question HERE. 

If God is understood as a necessarily existing being (and not a contingent being like us, e.g.), then God cannot not-exist. If something cannot not-exist, or necessarily exists, then it is simply logical nonsense to ask the question "What caused this necessarily existing being to exist?"