Kant proclaimed that all theodicies must fail in ‘On the Miscarriage of All Philosophical Trials in Theodicy’, but it is mysterious why he did so since he had developed a theodicy of his own during the critical period. In this paper, I offer an explanation of why Kant thought
theodicies necessarily fail. In his theodicy, as well as in some of his works in ethics, Kant explained moral evil as resulting from unavoidable limitations in human beings. God could not create finite beings without such limitations and so could not have created humans that were not prone
to committing immoral acts. However, the work of Carl Christian Eberhard Schmid showed Kant that given his own beliefs about freedom and the nature of responsibility one could not account for moral evil in this way without tacitly denying that human beings were responsible for their actions.
This result is significant not only because it explains an otherwise puzzling shift in Kant's philosophy of religion, but also because it shows that the theodicy essay provides powerful evidence that Kant's thinking about moral evil and freedom underwent fundamental shifts between early works
such as the Groundwork and later works like the Religion within the Limits of Mere Reason.