> But imagine a world in which Newton ... built a complex machine that, given the relative positions of a set of planets, could work out their subsequent trajectories..

Thanks for the reply, I see what you're saying. Just to get metaphysical though, can't one argue that that's essentially what Newton did? Granted the machine he made was mathematically elegant, and the study of its components has been fruitful, but nonetheless it's the nature of physics that one never knows whether a formalism is really describing what's going on, or whether it might someday be superseded. Can we not imagine, say, a future where the art of warping spacetime is so well-understood that Newton's theories about a gravitational "force" are seen as just a bit of predictive machinery - useful for making approximations, but bearing no connection to the "truth" underneath?