Monday, July 27, 2009

David Lewis and Newton's Challenge, (or the relationship between science & metaphysics)

By "Newton's Challenge," I refer to the fact that after the Principia’s success the authority of "science" has been used to settle debates within "philosophy." I distinguish among three different but closely related versions of this challenge: (NC1) a philosopher claims that natural philosophy must be consulted in the process of doing metaphysics; (NC2) a philosopher claims that natural philosophy is epistemically prior to metaphysics; (NC3) a philosopher appeals to the authority of a natural science, which is in some sense (institutionally, methodologically) taken to be a non-philosophical source, in order to settle argument over doctrine. Much of my recent scholarship focuses on tracing out the development and crucial role of Newton's Challenge in the history of philosophy and science.

Sometimes "Newton's Challenge" gets resisted by philosophers. Here's an interesting and prominent example:

"...maybe the lesson of Bell's theorem is exactly that there are physical entities which are unlocalized, and which therefore might make a difference between worlds--worlds in the inner sphere--that match perfectly in their arrangements of local qualities. Maybe so. I'm ready to believe it. But I am not ready to take lessons in ontology from quantum physics as it now is. First I must see how it looks when it is purified of instrumentalist frivolity, and dares to say something not just about pointer readings but about the consitution of the world; and when it is purified of doublethinking deviant logic; and--most of all--when it is purified of supernatural tales about the observant mind to make things jump. If, after all that, it still teaches nonlocality, I shall submit willingly to the best of authority."--David Lewis Philosophical Papers, V2, introduction xi

Given the way I have formulated "Newton's Challenge," I just love Lewis' terminology ("submit," "authority"," "lessons in ontology," etc.)!
In a fascinating recent plenary lecture at BSPS in Norwich, Simon Saunders claimed that with the theory of decoherence, Quantum Mechanics now meets Lewis' challenge. If Saunders is right then philosophers of science have a club to beat the metaphysicians.


  1. At the very least, it would give naturalist metaphysics an argument besides parsimony-- completeness and empirical adequacy, here we come!

  2. I'm sure my take on this is not nearly specialized enough for this occasion, but I would prefer QM to remain a theory about the behavior of physical objects (matter writ large, i.e., reduced or converted into energy or sub-material particles as needed) and for it to be based on observation, i.e., for it to remain committed to accounting for the observations made during experiments (Lewis's "pointer readings", I presume).

    Metaphysics, by contrast, is a reflection upon the conditions of the possibility of objects (of experience). Metaphysical reflection cannot be directed at the results of physical experiments.

    When confined to science, instrumentalism is not frivolous at all. So since I don't think QM should seek "purity" (from instruments), and I agree with Lewis that it would have to purify itself in that way to teach us anything about ontology, I don't think submission is just around the corner. At least for me.

  3. Eric,

    I'm quite perplexed. Even if the decoherence approach did meet Lewis's challenge, I'm not sure how this would give philosophers of science "a club to beat the metaphysicians". Also, I'm not sure why philosophers of science would want to "beat the metaphysicians" or need "a club" with which to do so. (btw, I'm assuming all this is figurative, right? ;-)) Could you please explain?

  4. I think, coming from the right angle, it makes perfect sense. It definitely makes thinks significantly more interesting.

  5. Gabriele, yes only (causally inert) *abstract* clubs allowed into our club!
    I am alluding to the fact that much metaphysics inspired by (in) David Lewis' program seems to presuppose localization and, more generally seems unconstrained by knowledge of recent physics (there are exceptions, of course).