Hi Matthew and John,

I have no training in philosophy or theology, but I found your article helpful in my personal journey to understand the doctrine of the trinity better. I have a question about the definition of ‘nature’ in your paper. You say:

Predication in the strong sense: ‘x is y’ = df. x is an integral aspect of the primary substance y and the nature of x is that of y. 

What do you mean by ‘nature’? In theological discussions I think of a nature as a secondary substance, i.e. a set of essential properties. However if I use this definition in your paper, strong predication implies y has the same essential properties as x. In other words, strong predication implies weak predication. If so, we run into the problem the article seeks to avoid: multiple divine substances exist.

I can think of two possibilities to avoid this problem. Either:

  1. You define nature as something other than secondary substance. If so, what?
  2. x and y are the same primary substance but somehow are numerically distinct (have one or more different properties). This seems incompatible with my understanding of ‘primary substance’, i.e. numerical distinction means x and y are different primary substances, leading to a contradiction.

How should I make sense of this?



PS: If your model avoids the problem of tri-theism by having one primary substance, how can we have multiple selves who are non-numerically identical? I presume the answer may be along the lines of ‘an aspect of a primary substance is not itself a primary substance’, i.e the ‘selves’ are not ‘things’.



December 28, 2023

Dear MR,

I want to thank you for your thoughtful questions about mine and John’s article The Son of God and Trinitarian Identity Statements, published in the research journal TheoLogica. If you had not mentioned that you have no training in philosophy or theology, I would have assumed the opposite in light of your presentation of your excellent questions. A great benefit of “open access” research journals like TheoLogica is that published scholarship is made openly and freely available. This dissolves boarders between research scholarship and those in the general public who don’t have access to research libraries or journal subscriptions. That said, there can be a downside when journals saddle researchers or their institutions with the financial burden of publishing. TheoLogica threads the needle of making research articles freely available without shifting a financial burden to researchers. Therefore, I want to begin by commending the journal for its open access format.

Regarding your first question—what do you mean by nature?—I don’t want to be too picky here. So, let’s assume your description of a nature, as the set of essential properties that everything with that nature has. In light of how you think of natures, you raise your concern that my definition of predication in the strong sense entails predication in the weak sense. Given that, you think tri-theism follows, which would violate the monotheism taught in Scripture (e.g., Deut. 6). “In other words,” you write, “strong predication implies weak predication. If so, we run into the problem the article seeks to avoid: multiple divine substances exist.”

You’re correct that strong predication entails weak predication. However, this does not entail tri-theism. Put differently, although the premise is correct the conclusion doesn’t follow. For one, the claim ‘Jesus is God’ understood according to an is of predication in the weak sense does not entail tri-theism, but rather logically permits it. Essentially what the claim amounts to is a claim that Jesus is divine or has a divine nature. Both the strict monotheist and the tri-theist could make this claim, assuming they believe Jesus is divine. In other words, someone could say of any allegedly divine being that the being is divine if they think either (1) there is only one divine substance or (2) there are multiple divine substances. The claim that ‘Jesus is God’ according to an ‘is’ of predication in the weak sense leaves logical space for either, but that is not the same as entailing one or the other. If the claim entailed tri-theism, then it would rule out monotheism, but that is not the case.

My rationale for introducing what I call an is of predication in the strong sense is that it allows one to say more than weak predication, even though it allows one to say what weak predication implies as well. It goes further than predication in the weak sense while also incorporating it. By way of analogy, suppose you say “John is in California” and I say “John is in Los Angeles, California.” We are both saying that John is in California, but I am saying even more than that. The same is true for an ‘is’ of predication in the strong sense—it entails what an ‘is’ of predication in the weak sense entails, but it also says more. And that is precisely why it is valuable in trinitarian discourse. It refers not only to secondary substance, which predication in the weak sense does, but also to primary substance. A polytheist who also believes that Jesus is one of multiple divine substances could say ‘Jesus is God’ according to an is of predication in the weak sense, and so could the strict monotheist who believes Jesus is God. Essentially, they are both saying Jesus is divine, or has a nature that is divine. But the Christian monotheistic trinitarian is wanting to say that, and more. The words “the Son is God” in line fifteen of the Athanasian Creed entails that Jesus is divine, but they also mean something more than Jesus is divine, which an ‘is’ of predication in the strong sense allows someone to say.

When the Christian confesses in light of monotheism that Jesus is God according to an ‘is’ of predication in the strong sense, she is saying (a) Jesus is divine, but also (b) Jesus is the one being or substance who is God. Put differently, she is saying that Jesus is the very same substance (or internally unified being) as God the Father, and because of that Jesus has the same nature as the Father, namely the divine nature. However, she is not saying ‘Jesus is God’ in the sense of an ‘is’ of numerical identity that would entail that Jesus is the Father as if they are not distinct, which is inconsistent with church tradition (e.g., see the Athanasian Creed, lines 4-5, 24) and Scripture (e.g., see John 1.1, and the accounts of Jesus’s baptism—in Matthew 3.16-17, Mark 1.10-11, Luke 3.21-22—where all three persons are simultaneously manifested). The Christian who confesses Jesus is God according to an ‘is’ of predication in the strong sense can effectively say: everything that the Father is and the Holy Spirit is, the Son is, except the Father and the Holy Spirit.

In a follow-up email, you mentioned my “model” and ask a good question, which I added above as the postscript to your note. It is important to clarify that mine and John’s article does not present a model of the Trinity. The article simply clarifies the sense in which a trinitarian Christian can coherently claim that Jesus is God, while also affirming the same about the Father and the Holy Spirit while maintaining monotheism. Personally, I see no need for a model of the Trinity once the identity statements being made are properly understood. Models of the Trinity are sometimes presented to make sense of an apparent incoherence in the doctrine of the Trinity. But, as argued in our article, the apparent incoherence dissipates when the identity statements in orthodox trinitarian theology are accurately understood in light of the nature of a substance.

In the postscript, you hint towards the fact that substances can have distinct aspects, which is correct. There are many examples of substances with distinct aspects, which are not numerically identical to the substance but are nevertheless the substance they are an aspect of. Consider, for example, my chest. As a neo-Thomistic hylomorphist, I think my body is essential to my humanity and every part of it is en-formed by my soul (see Owen, 2021). From this framework, it is easy for me to say that “my chest is me,” according to an ‘is’ of predication in the strong sense. However, the claim that “my brain is me” is true in the same sense. But my brain and my chest are distinct and yet they are both me. They are the one substance that is Matthew Owen, but neither is numerically identical to Matthew Owen. Each part is Matthew Owen according to an is of predication in the strong sense, which entails the weak sense as well; but neither is Matthew Owen according to an ‘is’ of numerical identity.

We could give a similar breakdown of numerous substances throughout the natural world—people, dogs, cats, frogs, fish, etc. When I cite such examples, I make it evident that I am not making a special exception for the Trinity in my ontology. I am pointing out that there is nothing unusual about one substance having multiple distinct aspects that are the one substance they are aspects of. However, two points of clarification are necessary.

First, it is important to clarifying that these other examples are not meant, at least when I speak of them in this context, as models of the Trinity. Again, I think that once we properly understand the identity claims, we don’t need a model of the Trinity any more than we need a model to understand the claim that my chest is me. I am using such examples as analogies to clarify identity statements and their coherence—nothing less, and most importantly, nothing more. I agree with what Fred Sanders has written here, that analogies can make limited points pertinent to the Trinity, but we shouldn’t expect there to be an analogy of the Trinity as a whole.

Second, I use the analogy of other substances, such as the human body, to make the point that it is not unusual for there to be substances with distinct aspects that are the substance they are aspects of. However, what is unique about the Trinity, as far as I know, is that you have one substance that consists of three distinct aspects that are persons. Though unique, I don’t see anything logically problematic about one substance consisting of three persons. Nor do I know of any metaphysical reason why one substance cannot consist of three persons, even though human substances are single persons with very few possible exceptions (e.g., Krista and Tatiana Hogan).

Thanks again for your thoughtful question, MR! I hope you and yours enjoy the rest of this Christmas season, during which we reflect on our Lord who is truly God (according to an ‘is’ of predication in the strong sense) becoming truly human (according to an ‘is’ of predication in the weak sense).




Featured image: Stained glass window depicting the Trinity in three persons at Saint Martin Church, Courgenard, France (more details).