In the theology of the Trinity–with Christology, the most difficult and most central piece (or the whole?) of Christian theology–a distinction is made between the “immanent” and the “economic” Trinity. The immanent Trinity refers to the inner life of God enjoyed between Father, Son and Holy Spirit, without reference, that is, to creation, to time, etc. The economic Trinity, on the other hand, refers to God’s activity in the creation, for example, in the Father’s sending of the Son in the power of the Holy Spirit.
In twentieth century theology, as Trinitarian theology experienced a renewal, this distinction was the subject of much discussion. Particularly jarring was the dictum of Karl Rahner, who wrote simply, “The economic Trinity is the immanent Trinity and vice versa” (quoted in von Balthasar, Theo-Drama, vol. 3, 508, n.3). In a single, compact paragraph, von Balthasar sums up the importance of maintaining the immanent/economic distinction for Christian theology:
[W]hile according to Christian faith, the economic Trinity assuredly appears the interpretation of the immanent Trinity, it may not be identified with it, for the latter grounds and supports the former. Otherwise, the immanent, eternal Trinity would threaten to dissolve into the economic; in other words, God would be swallowed up in the world process–a necessary stage, in this view, if he is to fully realize himself. (Theo-Drama, vol. 3, 508)
In this amazingly dense paragraph, two very important truths are laid out. First, the economic Trinity is the “interpretation” of the immanent. In other words, the activity of God revealing himself to us through the prophets and apostles, and most definitively in his Son Jesus, “interpret” to us the inner life of God. For instance, when Jesus prays to the Father, as he often does in the gospels, we catch a glimpse of what the eternal life of God is like.
Second, the immanent Trinity is distinguishable from the economic–not that they are not one reality–because if we collapse the two, then creation becomes necessary. If Christianity is not to become Hinduism, this fatal misstep must be avoided. Creation is contingent, not necessary; in other words, it is a gift out of the free choice of God’s love. Creation did not have to be, and if it did not, then there would never have been an “economic” side to God’s Trinitarian life. Instead, Father, Son and Spirit would have shared each other’s life in perfect self-giving from eternity to eternity.