Justin M. Anderson (Seton Hall University), Mark Johnson (Marquette University), Atria Larson (St. Louis University) and myself are at the initial stages of setting up a “Thomas Aquinas and Canon Law. International Working Group” [T.A.C.L.]. The aim of T.A.C.L. is to bring together scholars of Thomas and of (medieval) canon law in order to trace and study the connections between these two fields.
In particular, medieval ecclesiastical law as a fount of Thomas’ own thought remains an important source which thus far has seem to be neglected. Yet, that body of law holds significant importance in Aquinas’s moral, sacramental thought, etc. Below one can read a first description of our project as it can also be found on our website https://thomasaquinasandcanonlaw.wordpress.com/
Scholars who are interested in exploring these connections or can provide us with suggestions and comments on how to move forward are invited to contact us!
“Thomas Aquinas and Canon Law. International Working Group” [T.A.C.L.].
For nearly a century now, scholars involved in the study of Thomas Aquinas’s writings have sought to unearth the historical dimensions of his thought. This has included both studying the development of his arguments, but also his sources. As the decades have progressed, we have learned much of his indebtedness to his own contemporaries, but also to Scripture, to Augustine, to the neo-Platonic authors, and most recently to his Jewish and Muslim sources. However, one historical source that is largely, if not all together omitted, is Aquinas’s understanding and employment of the medieval canon law tradition, in particular both that of Gratian and the papal decretals.
Recent findings, especially regarding his use of the decretal tradition on vows, scandal, and truth have revealed that in all likelihood, Aquinas – like others around him – was both aware of and sought to include the logic of certain papal decrees within his own writings. When Pope Gregory IX wished to compile all the previous compilations into a single work, he asked none other than Raymond of Peñafort, Thomas Aquinas’s Dominican confrère who would – it is said – one day encourage Aquinas to write the Summa Contra Gentiles. Peñafort’s work was published in 1234 and is known as the Liber Extra. While the 12th Century’s Decretum Gratiani easily serves as an early benchmark in the medieval canon law tradition, the Liber Extra likewise serves as a similar point of reference established just under twenty years before Aquinas would begin to write. Moreover, according to the explorations of authors like Leonard Boyle and Joseph Goering, one cannot ignore that both canon lawyers and theologians, especially those in the Dominican houses of the 13th Century, were deliberately concerned with bringing their thought to bear in a practical way in the form of medieval penitentials. Here again Peñafort looms large. The medieval manuals for confessors became a meeting place and, consequently, a conduit of mutual influence between theology and canon law. Of course, the penitentials need not be the only locus of mutual influence. The Leonine edition of Aquinas’s Super Decretalem notes Henry of Segusio (a.k.a. Hostiensis), the author of multiple commentaries on medieval canon law itself, as one of Thomas’s potential sources.
All of this points to a rich new field yet to be discovered. Still, in this nascent field questions abound. What or who were Aquinas’s influences regarding medieval canon law? With regard to what discussions, philosophical or theological, can we find Aquinas employing the decretal tradition? What, if any, secondary literature already exists in this regard? While our project is, at this stage, primarily focused on the influence the medieval decretal tradition had on Aquinas’s thought and writings, not to be ignored are the writings of other 13th Century philosopher-theologians who may also demonstrate the use of medieval canon law in their own thought, or by their writings have influenced Aquinas as a conduit. Furthermore, the causal direction may interestingly be turned around: what influence may Aquinas’s writings have had on later medieval canon law, decretists and/or decretalists? Certainly the role of John of Fribourg could prove instrumental here as well.
Both Thomas’s œuvre and the medieval canon law tradition represent massive sources of knowledge in their own right. Tracing connections will likely require a familiarity with both. While the demand of such a study can make the task appear overwhelming, it is precisely because both fields of learning are so important that the work will prove both fruitful and intriguing.
 Sancti Thomae de Aquino, Opera omnia iussu Leonis XIII P. M., Tome 40, Pars D-E (Romae, 1968): E, p. 6.
 Historians of canon law often make a distinction between “decretists”, who commented on Decretum Gratiani, and “decretalists”, who commented on papal decretals including the Liber Extra.