P
polytropos
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Well, my statement was a legitimate instantiation of the law. (Though that’s irrelevant, since we also have never observed a body on which no net forces act.)I looked at this for a while before seeing what imho is the problem. It is the pithy way that laws are stated (and in this case you unintentionally shortened it too far by omitting to say net forces). Newton’s first law applies to any and every object, with or without a net force acting, although it may not be much use if the net force is large or difficult to work out.
OK… I think most people here are familiar with Newton’s laws, but none of this really disputes anything I’ve said about what the form of our laws suggests about what they lead us to believe. Actually you seem to agree with me that it leads us to acknowledge an actual disposition in matter, a tendency to “keep on doing whatever it has been doing.” (Though this is consistent with matter having a “desire” in the Aristotelian sense, which doesn’t mean that matter has a mind and desires things like I now desire a cup of coffee. But I think you knew that.)The principle is that Aristotle was wrong, matter has no desire to move or to not move. Matter is inert, and when left to itself will always keep on doing whatever it has been doing.
So when sat in a fast moving car with a glass of milk, if the driver slams on the brakes then you keep going until stopped by your seat belt, and your milk also keeps going until stopped by the windscreen. The car may have been accelerating at the time, and so the net force was non-zero, but we care not, since that’s just how the law is expressed. If we want we can calculate that force and subtract it from the before and after.
We now know that the first law is limited to particular observers, but it still works for everyday use.
Yes, I think we are in agreement. Science is not in the business of correlating observations to resulting phenomena. It does that, but it aims to do more: explain. We posit entities (ie. generate an ontology) because we realize that law-like generalizations, being non-explanatory, are only useful to us if there is some underlying reality that they describe and which is itself explanatory.Newton proposes a phenomenon called universal gravitation, which he uses to explain planetary motion and why things fall. He explains how it works (within the confines of the data available to him) but not why it should be, and so leaves an open question.
Einstein proposes a phenomenon called spacetime, which he uses to explain what gravity is. He explains how spacetime works but not why it should be, and so leaves an open question.
Science is an exploration and there will always be another mountain to climb before we can see further.
As you note, explaining one thing does not explain everything. Often what you have invoked to explain the first thing itself will call for explanation (though not immediately). (We would need a good reason to call just any old physical entity self-explanatory or brute. For it would have to be absolutely distinct from all of the other entities we are invoking it to explain, or else why would we feel as though we should invoke it?)
I’m not aware of any metaphysicians who have ever tried to do that. Metaphysicians are not natural scientists, and metaphysics has never existed for the sake of natural science.Have there been cases, say post-Newton, where armchair metaphysicians have proposed a concept such as spacetime or quanta which later was useful in science? There is lots of pure math that later turned out to be useful in science, but I’m not sure the same can be said for metaphysics.