The theological and narrative contents of the Acts of Thomas have been investigated in several studies and monographs over the last two centuries, but little headway has been made into the question of the book's function in the religious communities in which it was used. Following the suggestions of François Bovon and Averil Cameron, this paper counters the common conception of the Acts of Thomas as a novel for the sake of generic edification and amusement, and argues that the book should be seen as having been, in some sense, Christian scripture. The centerpiece of the paper is an evaluation of the third act of Thomas, with particular attention to the Syriac text edited by William Wright. It is shown that the key themes of this act are the subservience of the human will to higher powers, and the philosophical concept of “natures” (F?s??/????). It is shown that the book coherently discusses these recognizable philosophical concepts, imparts salvation-historical significance to them, and explores them within a narrative framework. The narrative itself purports to contain historical details about the defeat of an ancient, significant foe, and the spread of the gospel in an unevangelized land. This scheme of theological discourses regarding salvation-history embedded within a meaningful salvation-historical narrative is explored as a mark of sacred literature. The essay concludes by discussing how a non-canonical work can be envisioned as Christian scripture.