This paper takes its cue from studies that point to the influence of Thomas Aquinas on the psychoanalytical theory of Jacques Lacan and explores key Lacanian themes of language, desire, God/the real, embodiment and gender from the perspective of the Summa Theologiae. To illustrate how a Lacanian perspective opens new interpretative possibilities with regard to the Summa, it focuses on language and desire, on the doctrines of creation ex nihilo and the incarnation, and on Thomas's attempt to incorporate gendered Aristotelian concepts of form and matter into Christian theology. It argues that it is possible to resist Lacan's nihilism, while allowing his psychoanalytical approach to language to bring about a deconstructive reading of Aristotelian philosophy from the perspective of Christian theology. This allows the reconciling paradox of the incarnation to challenge the dualism of form and matter inherent in philosophical cosmologies, to offer a more dynamic understanding of the significance of material creation and its incorporation into God by way of the resurrected body of Christ. A Lacanian approach brings to light hidden and neglected dimensions of Thomas's theology, making possible a postmodern Thomism, which offers a viable theological response to some of the most challenging questions facing theology today, around questions of language, desire, gender and creation.