In this study, I examine how Karl (in Swedish: Carl, in Latin: Carolus) Mesterton (1715‒1773) discusses and refers to earlier philosophy and theology in a dissertation De aeternitate Dei, ‘On the Eternity of God’ (1752). Mesterton was a professor of theology and a professor of logic and metaphysics at the Academy of Turku. He followed Wolffianism, which is based on the thoughts of the German philosopher Christian Wolff (1679‒1754). The research question is in what manner does Mesterton discuss and refer to earlier philosophy and theology in his De aeternitate Dei. This study is qualitative, and reflects how earlier philosophy and theology were conceived by Mesterton in the dissertation. In a broader context, the study is related to the question of how early modern research about the late antiquity and Middle Ages transpired in the Finnish territory in the eighteenth century. The conclusion of this study is that although Mesterton discusses and frequently refers to medieval theology and philosophy, he does not discuss medieval philosophy and theology in detail, and therefore his method of treatment is shallow. In addition, he shows no criticism; however, this was the usual practice at the academy.