Sola Deduction

December 22, 2006 § 8 Comments

Very interesting discussion on the development of doctrine at Sacramentum Vitae and An Examined Life. (Previous posts from both gentlemen are here and here, respectively).

Scott Carson at An Examined Life makes the argument (assuming I understand it correctly) that doctrine develops only by applying deductive reasoning to a body of formally revealed facts and principles which were finalized at the time of the Apostles. I’ll call this position sola deduction. Mike Liccione at Sacramentum Vitae makes the case that there is more to the development of doctrine than just logical deduction from preestablished premeses.

It probably doesn’t surprise any of my legions of regular readers that I come down firmly on the side of Sacramentum Vitae and against sola deduction. The reason I come down against it is that sola deduction is a specific case of a much more general error; a general error which some may have noticed is a personal bugaboo of mine, the windmill of my personal Don Quixote. That windmill is positivism.

If all valid doctrines follow from turning the formal crank of deductive reasoning on the raw material of facts and principles established at the time of the Apostles, and doctrines so established are not underdetermined by that deductive reasoning, then the Magisterium can be replaced by a computer.

But the situation for sola deduction is even worse than is made clear by Mike’s argument, though Mike’s argument is in my opinion sufficient for his purposes. If we accept sola deduction on its own terms as a thought experiment, we ultimately (though not trivially) end up with a logical contradiction. An assertion of logic alone is itself quite literally illogical.

UPDATE: Scott Carson fires back, finding my comments not merely unhelpful but singularly so. The most critical thing I should clarify is that when I characterize Scott’s argument as saying that doctrine only develops deductively, I don’t mean that the actual discovery of doctrines by actual particular persons proceeds only deductively as an historical matter. That would be a manifestly silly thing to claim. What I mean is that (as I understand the criteria) once discovered, genuine doctrines must be derivable without underdetermination by deductive reasoning alone from some original fixed set of doctrines (oral or written) existant at the time of the Apostles. The “without underdetermination” bit means that this deductive proof or theorem for a given developed doctrine, which though not necessarily explicit must at least exist in principle, settles the matter over and against any competing claims to doctrinal truth which are inconsistent with it.

If that is what he means, my criticism stands as written. And if that isn’t what he means by his claim that legitimate development of doctrine must proceed solely by deduction (as far as I can tell he uses the term “non-ampliative” to mean “solely by deduction” in the sense I just clarified) to “establish the truth of any particular inference to the [logical] exclusion of all competing, non-consistent inferences”, well, then I really have no idea what he does mean.

Oh, and everyone have a blessed Christmas!


§ 8 Responses to Sola Deduction

  • Anonymous says:

    Zippy:What you said in my combox puts it pithily enough: if Scott were right, then the Magisterium could be replaced by a computer.Best,Mike

  • zippy says:

    Thanks Mike, I “promoted” that comment to part of the post: I think it also fills in a few minor steps between what was (before the addition) my two final paragraphs. 🙂

  • <>It probably doesn’t surprise any of my legions of regular readers that I come down firmly on the side of Sacramentum Vitae and against sola deduction. <>It certainly doesn’t after you gave it a title beginning with the word “sola”. 🙂

  • CD says:

    I followed the little exchange between Mike and Scott with much interest, but for the most part, it left me puzzled, although I felt Mike had the upper hand, for the same reason Zippy did.When I attempted to find out what the eminent theologians thought, I discovered a very helpful article by Reginald Garrigou-Lagrange, which discusses the very question in Chapter 6: was surprised to learn that he seems to come out in clear favour of a deductive model of DD:“6b. Theology uses reasoning, illative in the proper sense, to deduce from two revealed truths a third truth not revealed elsewhere, that is, not revealed in itself, but only in the other two truths of which it is the fruit. Thomists generally admit that such a conclusion, derived from two truths of faith, is substantially revealed, and hence can be defined as dogma. Reasoning enters here only to bring together two truths which of themselves suffice to make the third truth known. The knowledge of the third truth depends on the reasoning, not as cause, but only as condition. [264].”And in 6c, he argues that the Church can teach a deduced doctrine definitively (although not dogmatically) even if only *one* of its premises is revealed, and the other is a truth of reason.If Garrigou has interpreted Thomas correctly here, he has successfully convinced me.

  • zippy says:

    Interesting comment CD. Unfortunately my time available to think about it and reply is limited at present and will continue to be so until the new year. (That includes even taking the time to read the article you linked to, which I will do ultimately but not immediately). But if it turns out that the “truth of reason” in that model does not necessarily obtain <>purely<> through deduction all the way back to primordial premeses from the time of the Apostles then the DD model isn’t actually <>purely<> deductive. That the last combinatorial step of some truth of reason with an existant revealed doctrine to produce a developed doctrine must be logical and unequivocal is I think something we can all agree upon. But that isn’t the same as ruling out all forms of reasoning other than deductive reasoning in the verificaiton of the truth of that doctrine, it seems to me.

  • Rob says:

    Zippy–It’s not that the magisterium can be replaced by a computer; it’s that the magisterium can be replaced by any well-educated, intelligent, and *religious* individual Christian who accepts the grace that opens the heart to understanding.

  • William Luse says:

    I know several “well-educated, intelligent, and *religious* individual Christian(s)” who believe they have accepted “the grace that opens the heart to understanding.” They’re also Jehovah’s Witnesses. I keep telling them they’ve got it all wrong, sometimes even dropping the word ‘heretic’, but they just think I’m a tool of the magisterium.

  • Rob says:

    Well, up-side: better “they just think” you’re a tool of the Magisterium, than that they think you’re *just a tool* of the Magisterium, right?Anyway, Merry Christmas!

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