Laws before facts
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:
- The laws explain the non-nomic facts.
- If Y explains X, then X does not explain Y.
- If X grounds Y, then X explains Y.
- So the non-nomic facts don’t ground the laws.
And this is the second:
- The non-nomic facts are many and disparate; the laws are simple and few.
- Prefer metaphysical theories that are simpler and more parsimonious at the fundamental level.
- 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.
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