give up "at least one of the 'essential propositions' of their faith". Second, there is Mackie's statement that an all powerful God, in creating the world, could have made "beings who would act freely, but always go right", and third is the question of what choices would have been logically available to such a God at creation. Plantinga built his response beginning with Gottfried Leibniz' assertion that there were innumerable possible worlds available to God before creation. Leibniz introduced the term theodicy in his 1710 work Essais de Théodicée sur la bonté de Dieu, la liberté de l'homme et l'origine du mal ("Theodicic Essays on the Benevolence of God, the Free will of man, and the Origin of Evil") where he argued that this is the best of all possible worlds that God could have created. Plantinga says we live in the actual world (the world God actualized), but that God could have chosen to create (actualize) any of the possibilities including those with moral good but no moral evil. The catch, Plantinga says, is that it is possible that factors within the possible worlds themselves prevented God from actualizing any of the worlds containing moral goodness and no moral evil. Plantinga refers to these factors as the nature of "human essences" and "transworld depravity". Across the various possible worlds (transworld) are all the variations of possible humans, each with their own "human essence" (identity): core properties essential to each person that makes them who they are and distinguishes them from others. Every person is the instantiation of such an essence. This "transworld identity" varies in details but not in essence from world to world. This might include variations of a person (X) who always chooses right in some worlds. If somewhere, in some world, (X) ever freely chooses wrong, then the other possible worlds of only goodness could not be actualized and still leave (X) fully free. There might be numerous possible worlds which contained (X) doing only morally good things, but these would not be worlds that God could bring into being, because (X) would not be free in those worlds to make the wrong choice. An all knowing God would know "in advance" that there are times when "no matter what circumstances" God places (X) in, as long as God leaves (X) free, (X) will make at least one bad choice. Plantinga terms this "transworld depravity". Therefore,