Stephenson:Neal:Quicksilver:688:hypotheses non fingo (Steven Horst)

From the Quicksilver Metaweb.

The date at which the book has Newton come forward with "hypotheses non fingo" may be anachronistic. This phrase first appeared in the general scholia of the second edition of the Principia; and as I understand it, it reflected a good deal of agonizing over what to think about "forces" between editions.

This is, I think, an enduring problem in the interpretation of laws, and lives on in another form in the realist/empiricist debate in philosophy of science.

What is it that a law expresses?

==Is it a description of how all objects actually behave? (No -- taken singly, and interpreted as universally quantified claims about objects and events laws, such as the gravitation laws, would be FALSE, as objects are really governed by a combination of forces and hence never behave as just one law says. Cf. Nancy Cartwright's HOW THE LAWS OF PHYSICS LIE, 1983, Cambridge U.P.)

==Are laws idealized claims about actual behavior?

==Claims about how objects WOULD behave if only one force were at work? (No, because they say something about how objects behave even when multiple forces are at work too -- they capture "real invariants", if you will.)

==Well, then, do they really say something, not about kinematics but about FORCES? (Leibniz) If so, it sounds like one is committed to an ontology of forces. Not necessarily an awful idea, but then you have a science that is in the business of positing kinds of things that cannot be observed, and fattened your fundamental ontology in the bargain.

==Are they dispositions or capacities of objects? (Cartwright) Well, but what is a "disposition" or "capacity" -- here you are back to something like positing essences.

I tend to see both Newton and Leibniz as being a bit ambivalent here. Newton, of course, DOES talk about forces (and does frame hypotheses, and even CALLS them hypotheses). The "hypotheses non fingo" quote -- made a centerpiece of some Newtonian philosophers like Hume, and later picked up by the Behaviorists in psychology -- is in the not-positing-unobservables camp. But he seems to favor views at other times that emphasize essential natures and even tends towards forms of vitalism, not only about plants and animals, but minerals. (Dobbs and Jacob's NEWTON AND THE CULTURE OF NEWTONIANISM is good on this, though sadly out of print last time I checked.)

Leibniz also seems ambivalent to me. As a physicist, or perhaps a philosopher of physics, he rejects the fundamental-ness of the idea of extension in favor of making "force" fundamental. There is a way of interpreting this as a re-situating of mechanism rather than a rejection of it, as Leibniz the character in QUICKSILVER intimates. But the Monadology adopts this panpsychist gloss on "loci of force", and (on metaphysical grounds based in an interpretation of the traditional definition of 'substance' as "that which exists independently") concludes that monads cannot interact causally, which seems utterly incompatible with mechanism.

Likewise, both Newton and Leibniz employ God for part of the explanation: Newton appealing to special providence (sometimes to solve physical problems like why the planets stay in orbits more perfect than he thinks they should, given (a) gravitational interaction between planets and (b) the supposition of an ether which should cause friction), and Leibniz general providence (making it so the perceptions of the different monads line up to create the illusion of a shared world and agent causation on the part of monads).