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Ye Olde Trinity Diagram: The Shield of Faith

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How many times have you seen one of these offered as an explanation or illustration of the doctrine of the Trinity?

There’s a good article about these here, complete with some links to real medieval examples. Basically, this sort of Shield of Faith (Latin: scutum fidei) diagram seems to have originated in the high middle ages, with the intention of illustrating the doctrine.

In general, I love diagrams and visual aids when it comes to philosophy and theology. But rather than getting you nodding, though, I think this diagram ought to get you scratching your head. We should ask: what does it mean? How, that is, are we to read this chart?

We naturally assume that “is” (est) means the same thing all around. What then, does it mean in the negative parts, e.g. where it says that the Father “is not” the Son. Presumably, one has noticed that some things are true of the Father, that are not true of the Son, and vice versa. By the distinctness of discernibles then, the chart is implying that Father and Son are not numerically one.

So far, so good. These three claims of the outer ring seem plausible. Now we turn to the positive parts. (“The Son is God.” etc.) Doh! Does anyone see a problem here?

Sorry to bore the philosophers and logicians out there, but permit me spell it out. Identity is by definition a transitive and asymmetric relation. So these two claims

  • The Father is God.
  • The Son is God.

imply that

  • The Father is the Son.

But on the outside of the chart, that very claim is denied. So the chart, on this interpretation, is asserting contradictory claims: for each of the Persons, that Person is, and isn’t, identical to each of the others.

Now it must be said that this contradictory interpretation is fine with some people! Its supposed to be a mystery, after all, and many mean a “mystery” to be an apparently contradictory doctrine.

The author(s) of the wikipedia article, though, draw a different conclusion:

Of course, if the diagram is interpreted according to ordinary logic, then it contains a number of contradictions (since the set of twelve propositions listed above is mutually contradictory). However, if the three links connecting the three outer nodes of the diagram to the center node are interpreted as representing a non-transitive quasi-equivalence relation (where the statement “A is equivalent to C” does not follow from the two statements “A is equivalent to B” and “B is equivalent to C”), then the diagram is fully logically coherent and non-self-contradictory. So the medieval Shield of the Trinity diagram could be considered to contain some implicit kernel of the idea of alternative logical systems.

The point here is: maybe the “is” in the chart shouldn’t be read as numerical identity. Whatever relation it is, it must be non-transitive – then, the doctrine embodied in the chart has a hope of being consistent. The million-dollar question, then, is what exactly is this “quasi-equivalence” relation?

In recent literature, there are a couple of closely related answers:

  • Michael Rea and Jeff Brower have suggested: “is constituted by“. So, for example, the Son is constituted by God, but is not constituted by the Father. What is “constitution”? Something analagous to material constitution – the relation between this mass of clay and this clay pot. See this paper for a nice, readable discussion. Professional philosophers (and not many others!) will want to see this, fuller discussion.
  • Relative identity. This goes back to Peter Geach, A.P. Martinich, and others, and has recently been defended by Peter van Inwagen. Even though he’s against it, I suggest looking at Rea’s paper here for an introduction to this approach.

Both of these approaches result in a consistent trinitarianism, although other sorts of objections will crop up.

Back to the diagram, the best that can be said about it, is that it illustrates the problem of finding a self-consistent expression of “the” doctrine. A chart like this puzzles rather than informs, which can lead to a more developed, and possibly a believable version of the doctrine. Or it can lead to embracing an apparently contradictory form of the doctrine. But that’s another topic.

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8 thoughts on “Ye Olde Trinity Diagram: The Shield of Faith”

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  3. Hi Michael,

    Thanks for your comments. Please jump back in to the discussion some time (soon?) when I post on their constitution theory of the Trinity. Below are some quick comments on your comments.

    They’d say that one thing that separates lumps from statues is that lumps, but not statues, can survive a massive change of shape. IF there are such things in the world as lumps, that seems reasonable. You’re right that many will choke on the claim that two material objects (a lump and a statue) can exist in one place at one time, but I guess they’d say that that’s just a price of solving the metaphysical puzzles they’re concerned with. And they really do want to say that the Athena-shaped lump of bronze and the Athena statue are two different things (they’re not identical, in the technical sense – see my previous posting on “Identity”), although they’re “numerically identical”. In my view, you’d be right to be suspicious about this claim.

  4. I have just read Rea and Brower’s paper on Material Constitution and the Trinity. Its flaw seems clear to me, but I am a novice philosopher.

    R & B say that the lump of bronze which occupies the same space as a statue is not the same thing as the statue, because a melted lump would still be a lump, but a melted statue would not be a statue. The problem with this argument is that while the term ‘lump’ would still apply to the melted material, it would not be the same lump. R & B beg the question by applying different criteria of sameness to the statue and the lump.

    Intuitively, it seems strange to say that a space is occupied by both a statue and a lump. These things look more like different ways of describing the same thing. Some attributes of the statue-shaped lump, including its matter are invariant under the melting transform. Others, including its resemblance to Athena are not.

    To my mind, it looks as though this attempt to tiptoe around the concept of identicality just looks like saying, ‘Father, Son and Holy Spirit all have divinity, so they are one’.

    A more rigorous look at that statue, by analogy with ‘seated-socrates’ would have required R & B to say ‘Athena-shaped-lump-of-bronze’, rather than just plain ‘lump of bronze’. This would have made it quite clear That the statue of Athena and the Ahtena-shaped lump of bronze are exactly the same thing.

  5. Triessentialism attempts to solve the problem of what exactly the difference is between the Persons of the Godhead.

    I’ve come to the conclusion that each of the Persons is constitutionally different (a different “substance”) but ontologically identical.

    A clay pot, for example is made of clay, its shape is clearly defined, and its purpose is to be a container. Without one of these three, it ceases to be ontologically a clay pot. There are clay containers, things made of clay in the shape of a pot but not a container, and pots in that shape not made of clay.

    I consider the shape and the purpose to be as much a part of making it a clay pot as the clay itself, and yet we cannot hold or touch “shape” itself or “purpose” itself. Neither is material, though both are embodied in the physical form of the cup.

    (In Triessentialist terms, the shape is Logical and the purpose is Emotional.)

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  7. Greek philosophy started to be imported to deepen the understanding of many aspects of Christianity almost from the very beginning…

  8. In regards to NT Theology, how could any first century Jew (the writers of the NT) come up with these ‘alternative forms’ of logic that have been invented in the intervening hundreds of years?

    Furthermore, if they even were familiar with these forms, what proof do we have they used them to express their ideas? And still does the Bible even suport this quasi-equivalence idea? Isn’t it much easier to stand on the Bible believing that Jesus is the human Messiah sent from YHWH? Easier to stand on the Bible, but tradition will cut your head off. We’re always answering the questions “Should I listen to you(Pharisees/tradition), or God”?

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