Dear philosophers-physicists, As it turns out, I will not be able to make the first meeting of the philphys reading group on Tuesday. (I should have no problem attending future meetings.) But, since I read Wilson's article, I figured I would go ahead and give y'all some of my comments and questions, which may help foster discussion. (What I say here may give the impression that I was not impressed with the article; that impression would be correct.) 1. I found the discussion of Newton's Second Law in section 2 particularly disappointing. Given that Wilson in several places makes reference to Newton's own views on various matters, I find it incredible that he did not discuss Newton's original formulation of the Second Law, which is *quite* different in important conceptual and mathematical ways from the more familiar, Eulerian F=ma. Most importantly, and to speak somewhat anachronistically, Newton's formulation is an integral equation, relating integrated acceleration to what we would today call impulse. This is particularly important in the context of several questions Wilson does discuss, as it allows for the consistent treatment of the collision of perfectly inelastic point particles, which F=ma does not. There also should at least have been mention of the issues that depend on the class of mathematical functions one will accept as representations of possible forces. If one allows, e.g., distributional forces, then one can get discontinuities even in the time-evolution of the position of a particle, not just its velocity and acceleration. And yet, for many purposes, it seems difficult to do without distributional forces, at least for pragmatic reasons. 2. section 3, p. 6: Wilson is just wrong that Newton "had no notion that energy conservation holds." The last paragraph of the Scholium to the Laws in *Principia* very clearly states a conservation principle for energy, though, obviously, Newton does not describe it as such. 3. section 4, p. 8: I have no idea why Wilson says that, on the point-mass approach, "it becomes difficult to see how Newton's laws could be shown *false*; at best, they might prove an *inconvenient* series of approximations to utilize." Putting aside the fact that Wilson must have meant "at worst" and not "at best", he seems here to be doing nothing more than advertising his well known predilection for---prejudice in favor of---continuum readings of classical mechanics. He makes no real arguments in favor of the claim, and there seems to be an obvious counter-argument: if finer and finer approximations turn out worse and worse, then the most natural reaction would be to reject Newton's laws as false. 4. section 5, p. 9: I find his discussion of the supposed incompatibility of the point-mass approach and the existence of constraints to be, at best, baffling, and, at worst, deeply confused. His claim that the wire must be able to "see" the bead's velocity before the bead approaches a given point, in order to know the force needed to keep the bead on the wire as it passes that point, is just the deeply mistaken teleological reading of Newton's Second Law. The wire doesn't "know" or "see" anything. If the bead stays on the wire as it passes a given point with a given velocity, then we know the force the wire exerted on the bead at that point. That's all there is to say. And, in any event, even if one were to be able to make sense of what the hell Wilson is talking about here, *nothing* in the discussion indicates that it is in any way peculiar to the behavior of *point-masses*. If there is a real problem here, it arises for extended bodies as well. This is just, once again, Wilson's irrational prejudice against pointilliste readings of classical mechanics. (It's not that I'm a particular fan of pointilliste readings of classical mechanics---it's just that nothing Wilson says against them seems cogent or relevant.) 5. section 5, p. 11: "once the basic 'particles' of mechanics are granted any spatial extension at all, they are likely to lose their postulated rigidity"---Wilson seems to assume without argument or remark that this is a bad thing for the 'basic-particle' view. The only reason I can see for his thinking so is, again, his prejudice in favor of continuum-interpretations of classical mechanics. 6. section 5, p. 12: he says that, infinitesimal readings of F=ma, though common in textbooks, are a mistake, and that "the considered modern opinion" is that F=ma should apply only to extended parts of a continuous body. I have *no fucking idea* what he is talking about. First, I have read many works on classical mechanics, and I have never once seen that view expressed, by a physicist, by a mathematician, or by a philosopher---with the exception of Mark Wilson. I know he thinks highly of himself, but surely even he doesn't think that his saying so by itself automatically transforms a statement into "the considered modern opinion". Second, I don't even know what the view means. The only way I can begin to try to make sense of it is to interpret F and a in not obvious and highly unorthodox ways, and even then it seems highly likely that it just won't hold true most of the time, no matter what one does. 7. section 7, p. 14: The question that opens section 7 is silly. Nothing else. Why would any serious philosopher, historian or physicist think it is even a well posed question in the first place, much more one with an answer? E -- Erik Curiel Postdoctoral Fellow Munich Center for Mathematical Philosophy Lehrstuhl für Wissenschaftstheorie Fakultät für Philosophie, Wissenschaftstheorie und Religionswissenschaft Ludwig-Maximilians-Universität Ludwigstraße 31 80539 München, Deutschland http://strangebeautiful.com