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Laws before facts

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Does the universe come “facts first” or “laws first”? That is, in terms of metaphysical priority, do the non-nomic facts determine what the laws of nature are, or are the laws at the ground floor determining what the non-nomic facts are? (Or maybe neither grounds the other; I’ll ignore this view for now.) The best-known example of a facts-first theory is Lewis’s “best system” account: to be a law of nature is to be a member of the set of generalizations over the non-nomic facts that has the best balance of simplicity and strength. Here are two rough-and-ready arguments against an account like that. The first is the circularity argument I gestured at a few weeks ago:

  1. The laws explain the non-nomic facts.
  2. If Y explains X, then X does not explain Y.
  3. If X grounds Y, then X explains Y.
  4. So the non-nomic facts don’t ground the laws.

And this is the second:

  1. The non-nomic facts are many and disparate; the laws are simple and few.
  2. Prefer metaphysical theories that are simpler and more parsimonious at the fundamental level.
  3. So prefer laws-first to facts-first metaphysics.

The second premise is a methodological principle, rather than a general metaphysical claim (hence the imperative). It’s a ceteris paribus principle, and so the conclusion is a ceteris paribus conclusion: there is a presumption in favor of laws-first accounts.



Written by Jeff

April 18, 2009 at 6:57 pm

3 Responses

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  1. Hey,

    these arguments would have more force if the totality of non-nomic facts could somehow be reduced to, or explained in terms of, the laws. But that doesn’t seem plausible: fixing only the laws leaves a lot of things open. So I guess Non-Humeans usually take both laws and the mosaic of non-nomic facts as fundamental.


    April 20, 2009 at 2:06 am

  2. Hi wo, thanks for the comment.

    That’s a good point, but I’m not sure how much it undermines my arguments.

    The first argument seems to stand: even if the laws can’t (completely) ground the totality of non-nomic facts, nonetheless the laws’ role in explaining the facts (in whatever sense they do) seems like it would disqualify them from being grounded by the facts.

    The second argument is weakened, since the few, simple laws (probably) can’t serve as the whole fundamental level. But what about a theory where the laws, together with a small subset of the non-nomic facts are fundamental—say some initial conditions? (Furthermore, some people are inclined to include facts about the initial conditions among the laws—there are reasons to think our universe’s ICs are pretty regular.) That’s still favored by the second argument.

    Things don’t go as smoothly if there is indeterminism, though. I’m not sure what the best thing to say is. One place to retreat here is to allow each undetermined event a place at the fundamental level. (So, for instance, on a collapse theory of quantum mechanics, each collapse-event would be fundamental.) The danger is that it starts to look like these events might be all (or close to all) we need. (Bell considers a “collapse ontology” along similar lines.) Is there something better to say about this case?


    April 20, 2009 at 6:42 am

  3. […] came first? Laws or facts? Both approaches can be found in physics. I favor the idea that symmetries determine laws […]

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