The third Principle asserts God does not have a body nor could He. The last part of that idea is a powder keg of an idea in theology. Are there things God simply can’t do? For the Rambam the answer is a very clear yes. God cannot cease being Himself. He is the essence self actualization. Today, most people agree God has no body but begin to get a little fidgety with the second idea not realizing these ideas go hand in hand but many rabbinical authorities in history weren’t so open to this principle. Some even considered it heretical. For them, the defining aspect of God wasn’t actualization of being. Rather, they saw God as infinite possibility… which, included things like creating a rock He can’t lift but then lifting it anyway.