Dear Vesselin ,
Thank you very much for reading and commenting my essay! I enjoyed very much yours as well, and I am happy that you are visiting my page.
> why "science is only about the relations between things, not about the nature of things themselves."
The intention of scientists is of course to know the nature of things, not merely their relations. But their means are operational. I think a good example is the difference of approaches between Einstein and Minkowski. Einstein tried to understand and explain Special Relativity by operational procedures, rods, signals, etc. He used physical objects like rods and clocks, but as means to derive relations between lengths, durations, etc. Historically, this operationalism worked well, and led to the rejection of the "realist" position existing at that time, that aether explained electromagnetism. So Einstein came up as operationalist and aether theory was abandoned*. Minkowski's position is different. He proved indeed that reality is four-dimensional. So he put back reality in its place, and was not merely operationalist. But we can interpret this in two ways. One is that the four-dimensional objects Minkowski talks about are "matter", and the other one is that they are geometric entities. My position is that we know at least that they behave like geometric things. We don't know what is "matter", but we know what is geometry. But both "matter" and "geometry" are metaphysical concepts. People can agree on the Lorentz transformations, but some can interpret it as geometry, and others as matter having geometric properties. So science, to allow the exchange of ideas and independent verification, avoids making metaphysical assumptions, and relies on what can be shared. And operational procedures can be shared. As well, when we have theoretical explanations, we formulate them mathematically, but we don't go into the interpretation of the underlying nature of the things in our equations. The only time we do it is when we can describe things in terms of other things whose description we already have. This is why I say it's about relations, and can't go beyond them.
Take Minkowski's spacetime. It is a geometric space. This means it's a mathematical structure. A general definition of mathematical structure is given in Universal Algebra, in terms of sets and relations. Like a parenthesis, I don't quite like the term "universal algebra", because I see those rather geometrically, but this is a matter of personal taste. Anyway, my point is that Minkowski spacetime is a real element of the Theory of Special Relativity, and I take it in a geometric sense. As a geometry, it is a mathematical structure in the sense of Universal Algebra. So all there is about it is captured in the sets and relations. But the nature of the elements of the sets in themselves play no role in Universal Algebra, than to allow the definition of relations. In fact, Universal Algebra can be reduced to relations alone, by replacing the elements by 0-ary relations.
So we have the description of the world obtained from observations and making theories, as relations, and we have the underlying mathematical structure, which is also as relations. And ideally, when we will have the right theory, the two will be isomorphic. Whatever new we learn by operational means about the objects will simply add more relations. This doesn't mean that there is no underlying reality, no ontology. There is ontology. My claim is just that we can't put the finger on it by operational means, the best we can do is to find relations.
> With regard to "nothing of the nature of the things is accessible to measurement or observation," how would you explain the common view that physics does studies physical objects, not just their relations? E.g., we measure the locations of planets and the sun (even we see them directly or through telescopes!) I agree that we may never have absolute (full) knowledge about them, but physics does measure such objects (not only their relations) and in this way proves their existence. The word "planet" means to other people essentially the same thing (whether it is exactly the same or not, I think does not challenge the fact that we see and measure (all in perfect agreement) an object that we call a planet.
There is an object called planet, of course. It is not like the object is different to each observer, it may look different, but it is the same. We share the same reality. We even agree that it is made of atoms. And we agree that atoms are made of particles. And here is a place where we no longer know what is the nature of things. Particles, fields, wavefunctions, pure probabilities? This is another discussion. Einstein wanted here to keep having a realist description. But Bell's theorem, by using the very EPR experiment, shows that Einstein had to choose between a fixed reality at each time, and locality. But sorry, I divagate. When I say that we can't really know objectively the nature of things, I mean it in a much broader sense. I would say the same in a classical world. The object is there, Einstein criterion of reality is satisfied, but I would still complain that we can't know its nature. I think what I mean is that, to know the nature of something, there is no other way for that object to be, so that what we can measure and observe about it is the same. For example, consider a classical, Newtonian world, where all the elementary objects are balls, cogwheels, pins, etc, all made of steel. And suppose, for the sake of explaining what I mean, that all these elementary objects, identical in density, can't be broken or X-ray-ed. Suppose that there are "people" made of these things, and they try to understand that world. If these steel elementary objects are all there is in this world, can anyone know that they are made of steel? There is no notion of steel there, unless the people they call steel a particular organization of those objects. But they don't know what they intrinsically are. It could be anything, from cheese compressed well enough to have the same density and assuming it is unbreakable, to any other material. We can just call it "adamantium" or whatever. In such a world, we could never know the material. This is what I mean by "their nature". So the objects exist, they can be measured by comparing them to one another, their inertia can be measured, and what we would get are relations only. Nothing about their nature. Of course, we could analyze a planet in that world, and see that it is made of ultimate parts like these, but that would be the end.
> "And, of course, my favourite example that physics does deal with the nature of things - Minkowski's explanation of length contraction demonstrates that length contraction would be impossible if the worldtube of a contracting rod were not a real four-dimensional OBJECT (length contraction showed that the name "3D rod" was incorrect and we have no choice to call it "a 3D rod", because the rod turned out to be a 4D object). I believe this is most evident from the more visualized version of Minkowski's explanation - the thought (which can be made a real) experiments - an image is given on my essay's page in my response to Harrison Crecraft and H.H.J. Luediger."
You are right, of course. It is not the reality of objects that I doubted in my essay, but the "material" so to speak. Somehow, the material is immaterial to science, only the relations. I am using the word "ontology" or "nature of things" in this sense. I was doing this in my essay to make the case that there is something irreducible about consciousness. When people think they can understand consciousness, and it's just computation or processes, they usually make a lot of assumptions on top of what they really know. My thesis is that, once we remove those assumptions that color them, and let computation or what we call processes to be bare, it becomes clearer why this reductionism doesn't work. My personal view is that all there is is geometry+sentience. Geometry is the form, and the substance is sentience. Not sure if this choice of words is very suggestive. It can be compared with Russell's monism, although I am not sure that they are the same.
Cheers,
Cristi
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* Side note: Einstein's approach is very similar to how Bohr tried to explain the quantum world operationally, by relying on classical physical objects like the measurement apparatus. This may seem paradoxical, because Einstein changed completely the approach and opposed Bohr's operationalism, trying to understand reality instead. I think this is due to Minkowski, who showed that spacetime is real. Einstein, I think, was influenced by this, and this reconceptualization helped him to discover General Relativity, where the reality is curved spacetime, and also made him expect similar level of realism from Quantum Mechanics. While Bohr remained, paradoxically, faithful to the operationalist position similar to Einstein's original position. I know this reading of history is very personal, but I try to explain what I mean.
. When people get emotional, they tend to misinterpret and make quick judgments. But it's understandable