On the Theological Equivalency of East/West Trinitarin Models

Theologians are oftentimes too lax in getting clear on the types of claims they make. Take, for instance, the claim that the East and West made theologically equivalent claims about the Trinity, although they divided philosophically in their conceptuality about universals: The East assuming that a universal could be numerically one and multiply instantiatable, and the West denying this. Is it indeed true that the East and West make equivalent trinitarian claims?

Theoretical equivalency is understood differently on syntactical and semantic approaches. According to syntactical approaches, theories T1 and T2 are equivalent if they have, as their extension, the same or equivalent set of models. This syntactical approach to understanding theories and their equivalency was dominant through much of the twentieth century, and is oftentimes referred to as "the classical view" or "the received view." On this approach, a theory is a set of uninterpreted axioms in a specified formal language using a set of correspondence rules that provide a partial empirical interpretation to the theory by linking observable entities and processes to particular non-logical terms. A theory is true just in case its interpreted axioms are all true.

The semantic approach to understanding theories and their equivalency has developed over the last four decades. While syntactic approaches are interested in deducibility from axioms, semantic approaches focus upon the notion of "satisfaction." Objects which satisfy the axioms are models of those axioms. According to the semantic approach, the axioms comprise part of a theoretical definition. Whether or not such a definition is true of the world depends upon theoretical hypotheses. A theory is true just in case all of its associated hypotheses are true. In the words of F. Suppe, the semantic view "construes theories as what their formulations refer to when the formulations are given a formal (semantic) interpretation" (Suppe, The Semantic Conception of Theories and Scientific Realism, Chicago: University of Illinois Press, p. 4). This model-theoretic view identifies theories with the set of models that satisfies the theoretical laws of the theories. The models can be understood as being a pure structure: abstract entities and relations. Theories T1 and T2 are equivalent if and only if they are satisfied by sets if models M1 and M2 respectively, such that M1 and M2 are isomorphic to each other.

Applying this to the Trinitarian question, we might say that sentence "God is both one and three" is satisfied by two different sets of models, one employing a multiply instantiable universal, the other a property particular overlapping the compresent bundles of properties constituting the persons. If two separate sets of model structures satisfy the same set of Trinitarian propositions, these structures are equivalent and they are isomorphic with respect to each other.

It is ironic to find that East and West Trinitarian controversies may have been argued by people holding equivalent or almost equivalent Trinitarian views. Perhaps one is not making a different theological claim at all when "starting with the persons" or "starting with the essence." Maybe, in fact, the new social Trinitarianism is finally equivalent to older, more traditional Trinitarian positions.