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Tuesday, June 28, 2011

Identity and symmetry

DALE [TUGGY] SAID:

About identity, you ought to read some standard work on predicate logic. If you did this, you'd find that my def. is neither circular, nor vacuous, nor outdated, nor unclear. You're objections show that you are simply not clear on the concept.
= is a relation which necessarily whatever there is bears only to itself, and not to anything else. So it is a relation which must be reflexive.
By "identity" you mean qualitative similarity (not numerical identity), perhaps to a high degree. And maybe sameness in terms of structure specifically (hence, your talk of mapping).

This criticism is highly ironic. I’ve been using the concept of symmetry to model the Trinity. And that’s a natural association. After all, if God is a Trinity, then God has symmetrical properties, viz. equipollence, self-similarity.

But Tuggy says that’s inadequate because identity is a reflexive relation.

Well, what does he think a symmetry is, exactly? Symmetries are reflexive. That’s a defining feature of symmetries.

So if the Trinity is the type of symmetry (indeed, the exemplar), or relevantly analogous to a symmetry, then that coincides with Tuggy’s defining criterion of numerical identity.

If you explicate numerical identity in terms of reflexivity, then a symmetry meets the condition.

Perhaps he’d object to the comparison on other grounds, but since that’s been his central objection all along, it’s hard to see where he can go from here–except to backpeddle furiously. 

4 comments:

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  2. Well, Adam, that goes back to an earlier issue I had with Tuggy. What kind of identity does he have in mind? Logical identity? Metaphysical identity? Personal identity? Some of the above? All of these above? How are logical, metaphysical, and personal identity related? Is one nested in the other?

    What’s the right kind of identity for the Trinity? What’s the salient standard? Does the Bible pick out the right theory of identity to use for the unicity of God? Is symmetrical reflexivity the wrong type of reflexivity? Is that insufficient to capture what the Bible says about God?

    I don't see Tuggy moving the ball forward. I see him planting the ball where he'd like it to be, then sitting on the ball. That doesn't further the discussion. Rather, that takes for granted what's at issue.

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  3. Steve, ah yes... I'm backpedaling... away from someone who is untutorable.

    But because hope springs eternal: no, numerical identity doesn't come in kinds. It's the relation that of necessity everything bears to itself. So, it applies to the Trinity, divine persons - anything at all that exists.

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