Dan said: > Richard, if you are following this thread, I'd like you to know that I > am rather vexed with that post.
I think I like vexing people - it always eventually leads to challenges to my ideas and such challenges can only be a good thing. > Unfortunately, you asked questions that will take hours to properly > craft a response and, fortunately, its been a very busy few weeks. So, > I'll acknowledge that I owe you a good post (others too but you are > the best example) and reply here. That's okay. By the mysterious power of InterList Synchronicity, I've been involved in a similar discussion over on the Culture, where I'm under siege by people who think either that science discovers theories rather than invents them or else all scientific investigations of some field are strongly convergent (across cultures or even species) on one or a small number of possible theories. It's interesting that over there I'm making an argument against the "strong reality" of scientific theories and here I'm taking on the Kantians. I guess that sooner or later I'll have to try to articulate my views on these matters rather more carefully than I have in the somewhat sloppy expositions to date (and I'm going to have to try to think more clearly on them too, which entails learning a lot more philosophy than I currently know). Anyway, to be going on with, here's the core of what I think is my most significant message on the subject in the Culture's debate: ----------------------------------------------------------------------- Suppose we want to build an aeroplane. We can attach bits of metal, plastic, wire, wood, string and so on into almost any pattern (and fill up parts with aviation fuel or oil or whatever), but most of them are not planes. We have an objective test to judge whether some particular arrangement is a plane or not: if it flies then it is, and if it doesn't fly then it isn't. (I ignore for now the possibility of balloons and helicopters and rockets and such things.) Nevertheless, there are many designs that do fly: there are 747s and SR-71s and Vampires and Spitfires and Zeros and so on. I would argue that all of those are human inventions, because the constraints on the design do not reduce the space of possible designs to one or a few disconnected arrangements. If you want to argue that they aren't human inventions then go right ahead, but I think then you'll be forced to consider few or no things as human inventions. Now, I've been talking a lot in another thread about quantum mechanics so let me draw on examples from gravitation for a bit. Just as in the case of the planes, there are constraints on theories of gravitation: they have to explain all the experimental data. However, this isn't strong enough to pin us down to just a single theory. People might claim that general relativity is our best theory of gravitation, but they're making an aesthetic or historical judgement when they do, because there are lots of other theories that match the predictions of general relativity in the domains in which it's been tested but not in more extreme circumstances. For example, there the theory of gauge theory gravity invented by my research group, which is in every sense except for the aesthetic as simple as general relativty, and which matches all of its predictions under all current tests (it differs on predictions about topology). If we allow for theories with more adjustable parameters then we can consider the Brans-Dicke theory, which adds a scalar field which is generated by matter and helps to generate the metric. Then there's the Rosen bimetric theory, which introduces a flat metric in addition to the curved one. There are many other theories of gravitation. They all "fly". Perhaps general relativity flies like a Concorde and the bimetric theory barely gets off the ground, but they're all valid theories of gravitation - so in what way are they any less human inventions that the planes? (Actually things are more complicated that that. Even if god told us that general relativity was the one true theory of gravity, that still wouldn't pin things down enough for us to know that certain mathematical structures correspond to things out there in the universe, because there are lot of different formulations of general relativity. You might even be able to argue that these are different theories that can be shown to always make exactly the same predictions, but they are conceptually very different in that each has a different view of which fields are fundamental. It's as if the 747, Airbus and Concorde were all in some sense secretly the same type of plane.) ----------------------------------------------------------------------- Rich VFP Caught In The Crossfire
