Jonathan Morgan argues that Cyril of Alexandria's interpretation of circumcision provides invaluable insight into his complex doctrine of salvation. Spiritual circumcision - or circumcision of the Spirit - is a recurring theme across the extensive body of work he produced before the Nestorian controversy in 428. When Cyril considers the meaning and scope of circumcision, he recognizes it as a type that can describe a range of salvific effects. For him, circumcision functions as a unifying concept for various aspects of his doctrine of salvation such as purification, sanctification, participation, and freedom. But Cyril's soteriology cannot be understood in isolation. Thus, Cyril's discussions of circumcision often include correlative concepts such as hamartiology and Trinitarian theology. In this way, Cyril's discussions of circumcision illuminate important doctrines within his entire theological schema. Cyril's interpretation of circumcision as a biblical type also sheds light on his biblical exegesis. The author demonstrates that what Cyril does with circumcision substantiates the thesis that his Scriptural interpretation was shaped, in part, by his relationship with Judaism. Throughout his biblical commentaries, Cyril goes to great lengths to demonstrate that Jewish theology and practice are founded upon the "types and shadows" of the Old Testament instead of the spiritual realities that are fulfilled in Christ. Several scholars have recognized this significant feature of Cyril's exegesis and have explored the various "type-reality" relationships present in Cyril's writings. However, very little attention has been paid to the way Cyril's interpretation of circumcision further clarifies this aspect of his biblical interpretation.