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We can define an "electrical device" as a device that works with electricity etc. Suppose that the theory of electromagnetism would be proved wrong in the future. Would then make sense to speak about "electrical devices"?

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    It will not be proved wrong, at most it will be replaced with something that it approximates in the relevant range. And we still talk about heat flow and conductivity while knowing that heat is not a fluid, so there will be no need to rename electric devices either. But yes, scientific definitions are provisional and are replaced with more precise ones as science develops. They came with a more precise definition of a "planet" just recently, and Pluto was downgraded. – Conifold May 16 at 19:46
  • Hard to understand these downvotes. Although a bit clumsily put, this is a very legitimat question in the philosophy of science. Change the title to "Are specific concepts of objects temporary" or "Are categories for objects temporary". And put in the tag "philosophy of science". It is not about definitions. Read Kuhn: "The structure of scientific revolutions". – Clyde Frog May 17 at 6:44
  • @user3451767 I changed the topics. Thanks for the asnwer. – ado sar May 17 at 12:34
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    Definitions are conventions of a given language. Unfortunately words can be created or removed or modified from a language. Definitions should not be thought of as right or wrong or true or false. We can say a person is using the word wrong in a given context --not the word is defined wrongly. A word can be poorly defined in some contexts. So we have to live with how people use words in a given context. So if people decide to modify the definition to the term electrical device the speaker would have the obligation to specify the context he uses the term to avoid confusion. – Logikal May 17 at 14:26
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    Yes. You'll learn that when you get married. – J D May 17 at 17:09
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There are two philosophical points worth getting into here...

First, Wittgenstein would point out that when we 'define', we are creating a class designator (my terminology): e.g., creating the definition of an 'electrical device' doesn't define an object, per se, but defines the set of all objects that fall within our constraints. Further he'd note that all such class designators are 'family resemblances' other than identities. In other words, if you imagine a photo of a large extended family, with the grandparents in the center, and their children, grandchildren, cousins, nephews and such spread out to the left and right according to how closely related they are to the central figures, then as we scan across the picture we can see the family resemblance from one person to the next, but if we look at the leftmost and right-most people, they may look nothing at all alike. This allows concepts to drift — some members drop out of the picture, new members are added, new snapshots get taken — and eventually the original 'family resemblance' might be lost entirely. If electromagnetic theory were proven 'wrong' in the future, all that would happen is that we would start excluding devices that worked by the old principles and including new equivalent devices that worked by whatever new theory was developed; maybe we'd eventually change the name of the class designator, maybe not.

Second, time-conditions play hell with definitions, because definitions are (intuitively) atemporal. When we say something is an 'electrical device' we inherently presume that it was always an electrical device, and always will be. Nelson Goodman pointed out this problem back in the 1950s by inventing two new definitions: grue and bleen. Grue is the color of an object that is blue before some arbitrary but fixed date, and green thereafter; bleen is green before that same arbitrary but fixed date, and and then blue. His point is that it is logically impossible to tell whether an object is green or grue (or bleen or blue). If we buy a brilliant blue sapphire, how could we know whether we will wake up some morning and discover it's now a brilliant green sapphire, because it was actually (always) bleen, not blue. Adding time-dependent properties to our definitions really mucks with our capacity for induction.

Best not to head into this philosophical darkness. You are likely to be eaten by a grue.

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Newton's theory of gravity has been proved woefully broken. It has been replaced by Einstein's theory of gravity, also known as General Relativity.

Similarly, electricity and magnetism did not change their names when Maxwell developed his unified theory of electromagnetism, nor when Dirac developed a quantum reformulation or when the quantum field theorists redefined everything.

Yet another reformulation, such as a string theoretical one, will still not change the observed phenomena, nor what we call them. Only the underlying concepts invoked by the name may change.

In this sense, yes definitions are temporary. But not because we define a different thing, only because our understanding of the same old thing's nature changes.

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    Woefully broken? Got us to the moon and back. "In need of subtle revision for huge masses and extremely high speeds" is more like it, yes? – user4894 May 17 at 0:11
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    Ontologically it is woefully broken. It assumes Time and Space to be absolutes and invokes a magical action-at-a-distance. This is a philosophy forum not a spaceflight forum. – Guy Inchbald May 17 at 7:49
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    @GuyInchbald - Modern physicists don't usually assume theories imply any ontological facts beyond their quantitative predictions (though infinite speed of transmission is a prediction, and that one is wrong--but that just shows Newtonian grav. is an approximate theory that breaks down at high speeds). For example, the physicist Kip Thorne mentions in a book that there's an alternate mathematical formulation of general relativity which doesn't assume curved spacetime, and that it's just a pragmatic matter which version to use in what situation since both formulations make identical predictions. – Hypnosifl May 17 at 9:11
  • @GuyInchbald Relativity is woefully broken too, ontologically speaking. It can't explain dark matter or dark energy, it can't be reconciled with quantum theory. Ontologically it's wrong. As is every scientific theory. I hope you don't think science is some sort of ultimate truth, as opposed to a historically contingent approximation to the experiments we can do. – user4894 May 17 at 12:35
  • The ontological implications of a theory may not be of interest to physicists but they are to philosophers. This is not a physics forum either. Whether Relativity and/or QM are ontologically sound remains an open question and irrelevant to Newtonian mechanics. – Guy Inchbald May 17 at 13:45
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It seems to me that you question derives from the following reasoning

(1) one cannot define what does not exist (2) therefore, a defnition * presupposes* the existence of the definiendum (3) therefore, when the definiendum is proved not to exist, the definition looses its meaning.

I think premise (1) is questionable. However, I think it is correct to say that a definition presupposes the possibility of what is defined.


  • A definition, as such, does not require the existence of the definiendum to be meaningfull ( to have a sense). Witness : after having defined something, you still have to prove that it actually exists.

  • Let me define a "marswalker".

marswalker : a human person having walked on Mars before the 1st of january 2020.

The defining expression has a sense, you can understand it; you grasp a concept while you hear it. So " marswalker" is meaningful.

Since there is no person satisfying the definition, the denotiion of the terme " marswalker" is the empty set ( and the empty set is not nothing, it exists).

  • Also, note that a definition is a biconditionnal ( not a cetegorical statement) :

for all x [ ( x is a marwalker ) if and only if ( x is a human person such that...) ]

that is ( using the biconditionnal's definition)

for all x

(1) if x is a marswalker, then x is a human person such that ...

(2) if x is a human person such that ... then x is a marswalker.

As you can see , it nowhere says or implies that there are actually " marswalkers".


Note : here I use the distinction drawn by Frege between sense and denotation.

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  • you may edit your post in order to turn your question into a precise one and show you've done some research – user37859 May 17 at 16:05
  • note, my answer is perfectly standerd – user37859 May 17 at 16:06

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