To: Stuart B.
From: Geoffrey Klempner
Subject: What is a law of nature?
Date: 24th October 2011 13:53

Dear Stuart,

Thank you for your email of 14 October, with your essay for the University of London BA Methodology module, in response to the question, 'What is a law of nature?'

The issues which you grapple with in your essay, which I liked a lot, nicely dovetail with your comments on my response to your essay on Goodman's paradox. Let me lead in with that.

You're right, in a way, that any 'evil demon' universe is 'perverse' by definition, that is to say, it is clear by 'reason and logic' that there's something wrong which (we hope) isn't wrong with the actual universe. The actual universe (we hope) goes the way it goes, without interference or design. The beautiful thing about this picture is that we, as evolutionary products of a universe going the way it goes, naturally develop the ability to discern relevant patterns (epistemology naturalized), an explanation which would be impossible in any scenario where laws change or are interfered with in some artificial way.

I don't think this amounts to an admission that Goodman is wrong, or that his paradox has somehow been solved or refuted. We are relying on the language that we have, with the well entrenched concepts which we use, in order to artificially construct cases which are consequently infected with artifice all the way through. The situation is similar in a way to Quine's strictures on the indeterminacy of meaning/ inscrutability of reference. The examples (like gavagai=rabbit part) seem silly, because we literally haven't got the words to capture what the examples are gesturing towards.

In your essay on laws of nature, you talk about the basic laws of conservation (an idea whose power Leibniz was arguably the first philosopher to appreciate) where there is a logical necessity that we find *something* to conserve, as a condition for the very possibility of doing science. But why are the things that are conserved, the things that are actually conserved? Was it a merely logical error on the part of Descartes to claim that momentum, not energy is conserved (thus allowing mind-body interaction)? His contemporaries clearly thought there was something fishy going on. Yet it seemed to follow from Descartes' assumption that the laws of geometry capture the essence of 'extended substance'. As Leibniz pointed out, 'material substance' as geometrically conceived fails to account for the observed facts of impenetrability and inertia.

The logical extension of the claim that conservation principles lie at the base of the laws of nature is the idea that the universe exhibits certain fundamental 'symmetries'. This is the idea behind the Special and General Theories of Relativity, as I understand it. There is a powerful motive for thinking that there is some kind of necessity in the idea that the universe is maximally symmetrical. But we still haven't made an inch of progress, the Humean would say. If this isn't about describing God's mind (God being assumed to be a perfectionist who would naturally prefer maximal symmetry) then how, or the degree to which the universe exhibits symmetry, or obeys conservation laws, is ultimately just brute fact.

Necessity arises from two related ideas, both of which are very powerful: the idea of unrestricted universal generalization, and the idea of logical deduction. We have these, within a view of scientific laws which remains consistent with Humean strictures on necessity.

I fully agree with you that the self-styled 'necessitarians' merely label the problem. I also see your point that the difference in views can be explained in terms of the distinction between 'low-level analysis' (necessitarians) and 'high-level analysis' (Humeans).

But I'm left with questions. Why can't the laws of nature change? Is it just a brute empirical fact that they don't? Is it also a fact (about the future!) that they won't ever change? Why can't the laws of nature be different in remote parts of the universe? (You can run Goodman's paradox with space as well as time.) No lawgiver. Just a fact. It makes my head spin. How lovely it would be if you could prove the laws of nature from logic alone (the one, maximally symmetric set of laws). But then again, how could you ever prove this, how could you ever dictate to the facts in this way.

Possibly, you could have said a little bit more about why necessitarians merely 'label the problem'. As I said, I agree with this. Just a sentence or two would have been enough, just to cap the point.

All the best,

Geoffrey