ABSTRACT
A distinctive and original feature of Thomas on Christ's saving work is his application of concepts of efficient causality. Thomas maintains not only that God is the efficient cause of grace, salvation, and resurrection, but that God uses Christ's humanity and the sacraments as efficient instrumental causes. The explicit way in which he appropriates notions of causality from natural philosophy and applies them in theology is interesting today in part because religion always appropriates ideas from its secular context. Thomas establishes paradigms of causality by citing examples from everyday life or natural philosophy, and he shows how they fit the theological relationships that he wants to explicate. Scholars agree that Thomas attributes real efficient instrumental causality to Christ's human nature in the tertia pars of the Summa theologiae (1271-1273). Considered in the light of this consensus, what Thomas actually says about the instrumental causality of Christ's humanity in his later works may seem disappointingly meager, and his precise intentions unclear.
