The Reciprocal Interiority of the Divine Persons

In his presentation of Father, Son, and Holy Spirit, Thomas considered each person for themselves, within their own distinctive properties. The expository order of Trinitarian faith exacts this approach: in order to disclose the Trinity one must pick out what distinct feature characterizes each person as to his own incommunicable property. But a procedure which pictures the divine persons one after another does not constitute the last word in Trinitarian theology, because the divine persons exist and act inseparably, in reciprocated communion. This is why the treatise in the Summa comes to rest in a comparison of the divine persons (qq. 42–43). Its teaching about this re-engages the expositions given in the earlier studies of the processions, the relations and the persons, but this time takes them under the aspect of reciprocal communion, which is at the heart both of the eternal Trinity and of the working of grace for human beings, as central to the equality of the persons as it is to the persons' missions. This chapter considers the reciprocal presence of the divine persons (q. 42, a. 5). This question gives a real synthesis of the whole of Trinitarian doctrine, touching on both the eternal immanence of the persons and their activities in the economy. All of the features of Trinitarian theology return to us here, brought together under the sign of the unmixed distinction and unconfused unity of the Trinity.