As we dive into the particular contribution made by Rahner, to the topic of the Trinity, it is important to make a simple linguistic observation. Karl Barth spoke of the revelation and self-revelation of God. Rahner similarly attacks the correlation of these principles, but uses the more classical terms immanent Trinity and economic Trinity. In many ways Rahner is dealing with the same subject as Barth, but from a different angle. This is important to keep in mind, as it allows us to view both angles as complementary contributions to the doctrine. Rahner’s approach should be familiar at this point. These two conversation about the nature of the Trinity, are attempts at describing the state of the life of God, contingent upon the vantage point of the observer. In other words, when we view who God is, as he is revealed throughout history, we get one picture; when we view who God is, as he eternally exists within himself, we get another picture. Rahner’s axiom, which has already been stated above, shares the same intention as Barth, namely that “the economic Trinity is the immanent Trinity, and the immanent Trinity is the economic Trinity”. The God we get to observe in history, is then, according to Rahner, the same way God actually is. This moves the goal posts for the starting point of trinitarian theology. The simple yet profound shift introduced by Rahner, is to start the discussion about the Trinity at the most significant and definite point, namely: the economy of
salvation and the scriptures. What Rahner is basically arguing for, is a theology of the Trinity that is cohesive with experience and biblical narrative. To borrow a term from missiology, the missio dei (“mission of God”) is to provide and effectuate salvation for all to believe.
The biblical account gives good evidence that this mission is the work of one divine person. There is a certain singularity with which God operates in the world. For Rahner, the economic Trinity relates to the “biblical statements concerning the economy of salvation and its threefold structure”. Despite the complexity of the mystery of salvation, a single divine person can be discerned as its source, origin, and goal. This “previous knowledge of the economic Trinity, derived from salvation history and the Bible”, is the staring point for the process of systematic reflection. The immanent Trinity can therefore be thought of as a “systematic conception of the economic Trinity”. Rahner insists, contrary to many popular theological perspectives, that our experiences of God in salvation are real things; that our experience in the scriptures and in relationship with God testify concerning unity and complexity. That what we perceive about God, is actually true about God. In other words, although we experience diversity and unity within the economy of salvation, that diversity and unity corresponds to the way God actually is. Rahner states it the following way:
“The differentiation of the self-communication of God in history (of truth) and spirit (of love) must belong to God ‘himself’, or otherwise this difference, which undoubtedly exists, would do away with God’s self-communication. For those modalities and their differentiation either are in God himself (although we first experience them from our point of view) or they exist only in us.”
Echoing Barth in many respects, Rahner makes a case for an ontologically consistent view of the Trinity. Father, Son, and Holy Spirit are not mere descriptions of God as he is observed by us, nor are these revelation modalities which God utilizes at will. They are a truthful self-revelation or self-communication, consistent with the eternal divine being. The same God who appears as a Trinity is a Trinity.