This article argues that, without being reducible to a version of the Free Will Defence, Aquinas' theodicy and philosophical theology can offer contemporary versions of the Free Will Defence stronger metaphysical and theological foundations from which a response to Mackie's compatibilistic challenge – probably the most serious challenge against this defence – can be derived. Mackie's challenge to the Free Will Defence is the argument that the possibility of evil is not a necessary condition for the existence of free will, for God – if He existed and was omnipotent, omnibenevolent and omniscient – could have and would have created rational and free agents such that they would always freely choose the good. I claim, following Aquinas' hylomorphic ontology, that the creation of such a will is logically impossible as it would require the creation of a will containing naturally and invariably the formality of the universal and perfect good, and so the creation of a will indistinct from God's, which is by nature uncreated.
