What counts as “unique”? 25 Nov 2009 I’ve been thinking a lot lately about what makes something unique. Since Aristotle we have described something as unique if all its properties are special to it, but I don’t like property talk because I tend to think that it biases our thinking towards linguistic problems and solutions. I don’t have the property of weighing mumble kilograms, I weigh mumble kilograms. So wondering what “having the property of” denotes is, I think, just a mistake of language. When we try to set up our Kinds, natural or otherwise, what is it that we do? It seems to me that we use replaceability (or interchangeability from within the class, population or sample set) as the criterion for being “the same” with respect to some class. If you can replace any item of the class with any other item of the class, and make no difference (physical, logical, semantic, etc.) then both items are “the same”. A class is constituted by interchangeable items. But there are degrees of interchangeability and replaceability. Consider an electron. Any electron in the universe can be replaced by any other electron in the universe without changing the charge and mass, etc. of the atoms and molecular bonds they constitute. Time and location do not matter because the properties, at the physical level, are constant. Gold atoms are generally replaceable in the same way – atomic number 79 – but gold also has 18 radioisotopes of varying stability. So the class is interchangeable in the sense that the atomic number is invariant, but the other constituents of the atoms do vary, which means that they are not exchangeable without physical difference. So the class “gold” is a hybrid – partly replaceable and partly not. One might think, then, that “gold” is not a class, but that depends on what you assay. If you assay the number of protons, then it is a class. If you assay other things, like charge, mass, half-life and spin, then it is no longer a class. Science is the process of disentangling things you can group this way. Now consider a biological species. All members of Escheria coli or Felis tigris are interchangeable in some rough and ready ways. To a certain degree they all play the “same” ecological role (tigers are all predators, so far as we know), and they are all reproductively “the same” (tigers mate with tigers, except when they mate with lions). They even have “the same” morphology (that is, their homology states are shared). But we know that every individual in a biological species is unique. They are not wholly replaceable. Classes in the special sciences are less precisely defined by interchangeability. The items of their populations are distributed over different traits. If you replace one lion with another, it may do better or worse than its predecessor at defending territory, mating and such hunting as male lions do. Each lion is unique. It’s not unique like a snowflake, since the things that snowflakes do are largely unaffected by their different shapes*. It’s unique like an organism. Classification in special sciences thus is of a different kind to classification in the physical (general) sciences. Location in space and time matters. Each item is only approximately “the same” as other items in the classes of special sciences, because they are both historical and particularistic. This ties in nicely, I think, with Nancy Cartwright’s claim of the world being “dappled” and laws only applying roughly. We construct our classes as we progress in science, and each time we revise them, we do so on the basis of better information, more details used and occasionally the reconciliation of domains. A lot of the trouble people have with Millian Natural Kinds seems to me to be the identification of special kinds like species with general, or universal, kinds like subatomic particles or physical forces. * Although, if the principle is that physical differences make a difference, this cannot be entirely true. Biology Epistemology Natural Classification Philosophy Science Systematics
Philosophy My Absent Career 8: A second chance 22 Dec 20221 Jan 2023 So, at this point I am now 50 or so, doing my postdoc at UQ with Paul Griffiths, and living with my family just pre-separation (the divorce came a few years later). Two things happened. The first is that I started to gain confidence, Now, this may shock those who… Read More
History The first biological species concept 10 May 200918 Sep 2017 Before this text in 1686, the term species just meant some sort or kind of organism. It was a Latin word in ordinary use without much meaning in natural history, but then arguments began whether or not there were one or more species for this or that group, and so… Read More
You mention mistakes of language – and I think the problem you describe could be a problem of a similar kind (no pun intended). I’m inclined to think of everything in the concrete world as being unique. Take electrons – no two electrons are absolutely identical, at least according to quantum mechanics They might be functionally equivalent – i.e. practically interchangeable – but in an important sense they’re not identical. They’re each unique. Push that notion just a tad further, and I begin to think that things like Kinds are useful abstractions we place on the concrete world to order it for our purposes – namely, comprehension and use. No two gold atoms are perfectly identical, but they’re damn close enough that it makes no difference… to us. Same with species. Even if we agree there’s something universal about the Kind, ‘gold’ – that there are things that all ‘gold’ things have in common – that’s all good and well, but if it doesn’t strictly apply to the concrete world (because the Kinds apply to the concrete world in a vague way), well… we shouldn’t let ourselves fall in to a linguistic problem. That doesn’t diminish the usefulness of Kinds, nor of abstractions. But we can’t mistake the painting of a pipe for the pipe itself.
How do you mean that no two electrons are identical? In what ways, other than location, are they different? Kinds are formed on empirical differences (as opposed to kinds with a lowercase “k”, which are formed for convenience alone), and so they represent some real aspect of the world, ideally.
I agree that “same” doesn’t mean the same thing when applied to electrons as opposed to lions. Any two electrons in the same quantum state are seriously identical. Experiments that treat electrons as waves are so exquisitely sensitive that even the pimples on teenage leptons would create destructive interference patterns, or so they tell me. Meanwhile, even identical twins or individual copies of the same edition of a newspaper are easy to distinguish with a little effort. However. It has struck me as interesting that there seems to be a pattern in living things that becomes even more marked in cultural things, the emergence of mechanisms that produce, if not the identity of subatomic particles, at least the kind of interchangeability that composite objects are capable of. According to Heraclitus, everything flows, but from mitosis to sexual reproduction to education to Xerox machines, it appears that everything copies. I’m apparently the only guy who is struck by the fact; but isn’t it at least a little surprising that we think that rule is one exemplar and many copies, even though there are countlessly more kinds than there could ever be individuals? The extreme of this phenomenon occurs when a single scene, viewed from a single perspective and capturing a single moment, becomes endlessly reproduced as in the instance of the man who stood in front of the tank during the Tianamen Square massacre. That occurrence might appear to represent the apotheosis of an ultimate particular, but it was also an Andy-Warhol like tribute to the infinite multiplication of the same.
“Location in space and time matters.” In my subject what makes the location in time and space important is its performance context. This makes a difference and requires some thought. The issues I seem to be having is translating the way language is used in diffrent subjects into something workable. It appears to be the only thing making the difference with some issues I have had in relation to performance context and creativity for example.
I tend to think through this stuff multidimensional venn diagrams – as best as my 3D/4D model brain can handle.
A joke I once heard as an anecdote, possibly about Erdös: He was asked how to visualise a tesseract. He answered: “It’s easy. I just visualise a cube, and then I add a dimension.” Alles klar?
How do you mean that no two electrons are identical? In what ways, other than location, are they different? We could probably make infinite statements about any electron–not just location (which includes not just a vector plot but also a spatial relationship to other objects, all of which in the end are not absolute but relational), but also history (when it was formed, how long it existed, what happened around it.) These may not make a functional difference, but this courts a tautology since we are making positive statements about what the electron’s “function” is in the first place. (What is a lion’s function?) There may be a greater interchangeability among electrons, or atoms of gold, than among lions, but they each nonetheless represent an abstraction of experience, from which we build classes. (Interesting that you reject “having the property of X weight in kg” as an artifact of language, but not “weighing X kg” which also is; that is to say a finite (abstracted) description) of an inexhaustible object/process.) Another way of saying this is that we cannot experimentally replace one electron with another (I don’t think), so that when we talk about such replacements we are talking about theoretical (abstract), not actual (“concrete”), electrons, which by definition are identical, since this is the basis of the abstraction. Not a fair comparison with lions.
The title of your post reminds me of an essay by Asimov titled, “The Abnormality of Being Normal.” Roughly paraphrased and with respect to people and other organisms, Asimov notes that they are made of of many different parts and posses many different qualities or properties. Each of the parts and qualities exhibits some variation around a norm. While it might be reasonable to expect a particular part or quality to be at or very near the norm, it becomes harder to maintain the expectation as more parts and qualities are considered. The result is that the idea of a complicated organism, or machine or computer code being “normal” in the sense that its parts are all normal and working together normally becomes unreasonable. If the Good Doctor is correct, would that mean that being unique is ubiquitous?
The best sources I’ve seen on the topic of “same and different” are Douglas Hofstadter’s essays in his book METAMAGICAL THEMAS. In particular, I would recommend reading first ‘Analogies and Roles in Human and Machine Thinking’ and then ‘ Variations on a Theme as the Crux of Creativity’. If you’ve never read his work, or read it so long ago that you’ve almost forgotten it, I think you now will find his work an extremely useful resource in thinking about the concept ‘unique’.