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In Nature of Necessity (1974), Plantinga writes:

The distinction between necessary and contingent truth is as easy to recognize as it is difficult to explain to the sceptic's satisfaction. ...we must give examples and hope for the best.

Here he is speaking of so-called metaphysical necessity (even though he himself adopts the alternative label broadly logical necessity).

I'm interested in learning other views on how to make sense of metaphysical necessity. Can we really do no better than rattle off examples? At what point are the examples sufficient? For instance, if all I consider are examples of logical and/or mathematical truths, is that enough to get an idea of what metaphysical necessity is? That seems implausible. On the other hand, Plantinga for one seems to think that at some point no later than 1974, the variety of stock examples considered by philosophers became sufficient to capture a real and unambiguous concept of it. But of course, this doesn't strike me as very convincing, and I wonder if other philosophers take a different tack.

So, this leads me to the following.

Question. Would you guys please point me to some books/articles (other than Plantinga's) where metaphysical necessity is introduced and defended as a legitimate and definite concept?

Basically, I want to know if I'm being too skeptical and should just go ahead and accept Plantinga's approach, or if perhaps there are some trained, competent philosophers who share my skepticism and think we need to do a lot better than just reflecting on a few examples before barrelling off to study what could turn out to be a hopelessly ambiguous or even downright incoherent notion.

Please note that I am not asking for theories of modality. Perhaps we could say instead that I'm asking what it is exactly that theories of (metaphysical) modality seek to explain, and how we can be assured that there really is such a thing in the first place.

Thanks guys!

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  • As a starting point, you can see Varieties of Modality as well as The Epistemology of Modality. Feb 15, 2019 at 12:37
  • "what it is exactly that theories of (metaphysical) modality seek to explain" ? "some examples: St. Anselm : Necessarily: God exists. Descartes : It is possible for the mind to exist without the body. Berkeley : It is impossible for anything to exist unperceived. [...]" 1/2 Feb 15, 2019 at 12:41
  • "Philosophers have long been interested in how a modal claim can be known, justified, or understood. The philosophy of modality is the area in which one studies the metaphysics, semantics, epistemology, and logic of modal claims—that is, claims about what is necessary, possible, contingent, essential, and accidental. " 2/2 Feb 15, 2019 at 12:41
  • "Metaphysical necessity" is an ambiguous term. It has a purely technical meaning in Kripke's semantics of modal logic, a.k.a. "de re necessity", which can be made more precise. It is determined by "essential" properties and relations one keeps attached to the individuals when constructing possible worlds. Naturally, what is or is not essential, and in what contexts, is controversial, see essentialism. The non-technical traditional notion depends on what laws one believes metaphysically to hold, laws of physics, for instance.
    – Conifold
    Feb 15, 2019 at 14:24

2 Answers 2

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Kripke (naming and necessity) is often held responsible for reintroducing metaphysical necessity in contemporary philosophy. You'll find some examples from ordinary language in Naming and Necessity, that he uses to make his case.

Some philosophers are or were sceptical about metaphysical necessity. This includes notably classical empiricists (Hume), logical empiricists (Carnap, etc) and contemporary empiricists (van Fraassen, e.g. in Laws and Symmetry). What they typically reject is that there's necessity "in the world" as opposed to "in the head" or in language, so to speak. Their reasons are often epistemic (we don't have access to "other possible worlds")

The main purpose of metaphysical necessity is to account for modal discourse in ordinary language or in science. Modal discourse is ubiquitous. In ordinary language, this includes counterfactuals ("if I were rich, I would...") as well as dispositional terms (fragile, soluble). In scientific discourse this also includes talks of physical constraints, laws of nature, causality and explanations, which are all often analysed in counterfactual terms. Defenders of metaphysical modalities want to interpret this kind of discourse literally, as referring to genuine possibilities in the world, whereas sceptics think that it can be interpreted differently.

Kripke is famous for distinguishing a prioricity (e.g. analycity) and necessity, and thus challenging the once received view that talk of necessity could be identified with talk of a-prioricity. This was the received view during the first half of 20th century, when logical empiricism was dominant. One could say he moved back the burden of the proof on sceptics to explain how one could account for modal discourse without using metaphysical necessity.

It's not easy to analyse such basic concepts (beyond formal aspects: modal logic), apart from giving examples. The main reason why people accept it is that we always talk about unrealised possibilities, in a way that is distinct from mere logical, conceptual or epistemic possibilities.

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  • Thanks for the helpful answer. This is exactly what I was looking for. So I guess in order for metaphysical necessity to get off the ground, so to speak, we need us to really mean something (at least sometimes) when we use words like "necessarily," "could," etc. We also need to be able to group together some of these utterances so that the words mean roughly the same thing within the group. I'm not sure that's all true, but it at least seems more plausible to me now than it did before.
    – Ben W
    Feb 16, 2019 at 14:53
  • Kripke also distinguished aprioricity and analyticity, and it is hard to see how Quine, most fervent opponent of metaphysical necessity, would identify necessity with analyticity. I also do not see how the burden of proof is moved on the sceptics, if the point is to account for the talk of necessity it belongs to anthropology and linguistics, not metaphysics. After all, the talk of mathematical objects by mathematicians does not put on the sceptics the burden of disproving platonism, and those are more tangible than possible worlds.
    – Conifold
    Feb 17, 2019 at 10:26
  • Yes that's right. Whether it's always the same thing as you say is also contentious. There are different kinds of "could" (example I couldn't travel from Europe to America in 1 second given current technologies but I could given physical laws) but some think it's a matter of conditional modalities but the "could"are of the same kind. Feb 17, 2019 at 14:02
  • @Conifold Quine was suspicious about all kind of necessity but in "two dogma" he clearly associates analycity and necessity (and claim they both notions are as obscure). Kripke's arguments show that modal talk is distinctive and in need of interpretation, and a literal account comes out naturally. Feb 17, 2019 at 14:08
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    @Conifold you're right that it's an empiricist idea. I didn't want to imply that Aristotle or Leibniz held such view. It was the received view during the first half of 20th century when logical empiricism was the dominant philosophy. I will edit my answer to make it clear. Note though that I was talking about a prioricity, not analycity: this is broader and could include Hume (insofar as necessity boils down to relations of ideas). Feb 18, 2019 at 11:58
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Top Summary

No, metaphysical necessity is not coherent, and basically cannot be captured.

Background

Kripke's efforts to revive necessity as a valid concept in philosophy explicitly used the method of providing examples that intuitively felt to philosophers that they involved a "necessity" relationship. The necessity is not a "logical" one, so Kripke invented a weaker form of "necessity" to try to characterize what was meant.

Why do this?

The problem

Analytic philosophy was the dominant movement within philosophy for the 20th century, and the most clear articulation of it was from Logical Positivism. LP used absolutist definitions to justify its approach to philosophy, which was primarily logic based, and which treated science as a favored stepchild of logic. LP also used these absolutist definitions to try to banish most other approaches to philosophy.

However, non-analytic philosophers pushed aback against the LP attack, and the pragmatic empiricists in particular basically broke the LP movement. Popper showed that science uses refutations, not confirmations, and that all of science is radically contingent. This breaks the "necessity" needed to apply logic to this world. Hume was referenced in that objects in our world are "bundles", not reducible to the same entity over time, hence "we cannot step into the same river twice". So for our world, A=/=A, and logic cannot be applied to it. And Quine argued that as we each have to make guesstimated inferences as to what any language term refers to, all language is a personal inference, and A=/=A between any two language speakers so language also cannot support logic.

Quine argued that this broke the analytic/synthetic distinction, and that all knowledge was synthetic -- which most philosophers considered a step too far in his reasoning, but the A=/=A of language does not require accepting Quine's total breakdown of the distinction. And for any logic to apply to our world, there was increasing recognition that "identity" of an object requires it have an "essence", but essentialism is an Idealist concept, and the vast majority of philosophers have adopted physicalism as a worldview.

The consequence of this pragmatic empiricist pushback against LP, is that the applicability of analytic philosophy to our world was in question. Most analytic philosophers tried to adopt a "descriptive" approach to identity, where identity is established by some sufficient fraction of the descriptive elements applying. Kripke appropriately found descriptivism to be far too loose to support analytics -- as The Ship of Theseus and part substitution thought problems readily reveal (he spells out a set of critiques of descriptivist identity in N&N, which most philosophers consider decisive). So he set out to challenge the contingency of our world, in order to salvage analyticity.Kripke therefore set out to find a place for "essences" in contemporary philosophy.

Kripke's primary method to do this, was to offer thought problems that appeal to philosophical intuitions of their being necessarily true.

Empirical critique of Kripke

Kripke bases his argument on a variety of thought problems of identity, which he claims are necessary:

Water is H2O. Heat is molecular motion. Gold is the element with atomic number 79. Hesperus is Phosphorus cats are animals Samuel Clemens is Mark Twain

The first four of these all illustrate aspects of the same problem in Kripke's thinking, and that of most analytic philosophers. Kripke and analytic philosophers focus their study on MATH and LOGIC, not on science. There is a common assumption among analytic philosophers that even if events in our world are contingent, that there are unalterable LAWS OF PHYSICS behind them, and that those laws will fix the relationship between Water and H2O, and Gold and an elemental number.

BUT -- "laws" in science are not unalterable. They are not necessary, but are just regularities. They are the result of fundamental symmetries which were discovered in Noether's Theorem https://hackaday.com/2016/06/14/symmetry-for-dummies-noethers-theorem/. So -- "laws" are derivative, not primary. AND -- the symmetry that creates laws, is spontaneously broken, in every case, so our laws all have exceptions https://www.jstor.org/stable/41065.

Note, if neither laws nor symmetries are necessary, then the physical relation between things that Kripke lists cannot be necessary either. The intuitions of analytic philosophers on this question, are wrong.

Addressing his specific examples -- if the values of the constants of the Stannard Model of Quantum Mechanics were VERY slightly different, and per physics thinking, they are contingent, and COULD have been different, then H2O would not create the properties of water. Similarly, element 79 need not have produced the properties of Gold.

It would require some more complex change in the nature of physics for heat to not be the result of molecular motion, and it is hard enough for physicists to come up with tweaks to the Standard Model that even allow for any matter to appear at all, so an alternate physics speculation that produces a "heat-like" phenomenon that isn't molecular motion has not to my knowledge been developed, but there is no theoretical obstacle to this.

The details of orbital mechanics in our world would prevent two stable planets around the sun in Venus's orbit, and would not couple them to the Earth's rotation, hence in our world, we have discovered that Hesperus must be Phosphorus. But it would not require absurd tweaks to gravitation and our solar system structure to allow for a two planets to orbit in Venus's orbit and be stable for millennia, and some rotation rates of the earth could then lead to their being different. This identity too, is contingent, not necessary.

That cats are animals -- is subject to the problems of indefinite definition in our world. The margin cases for cats and animals are basically impossible to nail down, hence they are best understood as APPROXIMATE category terms, rather than logic categories. And that cats happen to be animals, was discovered by investigation -- it is possible in principle that mobile entities could be from other kingdoms. True, few plants are mobile, but they could be in principle, and the same with fungi. And these three kingdoms of multi-celled life HAPPEN to encompass the macro-scale life we have encountered, but there could in principle be lots of living things in the universe that do not fit any of our taxonomical categories, and cats could have been the first such discovery. That cats happened to fit into one of these three categories very well, does not make their fitting NECESSARY!

Kripke uses "modal reasoning" that resorts to "alternate worlds" thinking, but his "alternate worlds" are, in basically every one of these cases, insufficiently imaginative to actually encompass the alternate potential worlds considered by contingent science.

Samuel Clemems necessarily being Mark Twain was argued by Kripke through different means. He admits that Samuel Clemens may have had a different name, and may have been a very different person in "alternate worlds", and that somebody else could have written the Mark Twain stories. What Kripke argues is that the experience of selfhood is different for different people, and in these alternate worlds, that the "self" of our world's Samuel Clemens should be identified genetically, which could well be with other individuals who might be very different. Here Kripke has inapproprately gone reductionist, by coupling these other worlds to our Samuel Clemens by limiting him to the same parents and genetics. This reductionism does not fully capture our human intuition, or biological knowledge, as a few small genetic changes in Samuel Clemens would leave him VERY similar although not identical, such that a non-genetically identical Clemens could very plausibly have written the Mark Twain stories. And actually genetically identical Samuel Clemens in other worlds could have very different personalities and skills and may have been incapable of being the Mark Twain author. Most of our intuitions at that point would tend to lump that anyone who could authored the stories as "Mark Twain", and the genetically identical by non-author Clemens as not "Mark Twain" in any way. In this argument at any rate, Kripke failed to adhere either to essences OR to philosophic intuition.

So -- none of these examples are actually necessary, per the current conventions of scientific empiricism.

In additional discussion, Kripke tries to defend against Quine's point that A=/=A in word meanings between people, by arguing that people can use a Proper Noun properly (I.E. logically validly) without knowing all the details of the meaning of that noun. This argument relies upon their being an essence to the universe that the noun can refer to, without being fully cognizant of all aspects of it. The principle is plausible, provided that there is such an essence. How one gets an essence of "The Mississippi River" out of the bundle and variable nature of our world -- is still a problem for Kripke. He tried to put the burden on language, by assertion a "baptism" for such a term, and then learned usage through the community of speakers. BUT -- this still only justifies an approximate and fuzzy usage, not his "rigid designator" claim, and does not actually support valid analytic usage of any such proper name.

The pragmatic alternative

These empirical critiques, if appropriate, rebut metphysical necessity, and with it Kripke's justifications of analyticity. They leave our world entirely contingent, and analyticity inapplicable by its own standards to anything in our world, and to communication (language) between us.

This does not mean analyticity is useless. The pragmatic alternative is to accept that analyticity is not valid PER ITS OWN STANDARDS, but still can be useful, PER THE STANDARDS OF PRAGMATISM. There is a great deal of insight we can gain from applying analytic methods to our world, even if we cannot always trust its conclusions. We can communicate usefully, even without logical certainty of our shared meaning. Pragmatism does not demand necessity, nor certainty, only utility.

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  • +1 for gusto, however, you open claiming that the logical empiricists and positivists who were proponents of a form of scientism are the best example of analytical philosophers, and then go on to argue that analytic philosophers prefer to contemplate mathematics and logic to the general exclusion of science. So, which is it? Do analytical philosophers generally overstate or understate the importance of science? You can't have it both ways.
    – J D
    Feb 13, 2023 at 3:02
  • @JD Logical positivists believe in THE TRUTH and very clear and precise logical reasoning to arrive at it. Science, as it also in a pursuit to The Truth, is an allied activity, but lesser, a s scientists have to settle for only an approximation, not absolute truth. In contrast, pragmatists see analyticity as a rival to, and in conflict with, empiricism. This was the conflict between Popper and the Logical Positivists over how to do science. Popper won. BTW, this was a partial extract from a Kripke tribute, posted here: philosophy.stackexchange.com/questions/70563/on-reading-kripke
    – Dcleve
    Feb 13, 2023 at 5:05
  • I would argue that the Logical Positivists are primarily positivists in their outlook, and therefore their work on truth was an means to an end, that is to demonstrate what was real. Thus THE TRUTH served the subsidiary function of THE REAL, and therefore science was a greater activity than philosophy. In fact, they so went far as to declare philosophy and the pursuit of THE TRUTH as nothing more than an exercise in language, furthering the linguistic turn, though taking a wrong turn at banishing metaphysics which is unavoidable part of theory use and generation...
    – J D
    Feb 13, 2023 at 5:42
  • for the logical positivists, science IS epistemology, and language and the formal sciences are the handmaiden. That's why logical positivism is identified with the philosophy of science, and not the philosophy of reason. Carnap is famous for his ontological views supported by his views on existential quantification, not the other way around.
    – J D
    Feb 13, 2023 at 5:45
  • @JD -- Analyticity was the dominant form of academic philosophy when i was in school decades ago, and still is today. And academic philosophy is far the worse for that. But philosophy of science was and still is pragmatic empiricism, based on Popperian thinking. It was a wecome improvement in outlook. Popper fought the LPs over how to do science, and won. Discovering Popper in original texts well after graduating was a revelation, and tracing his transformation from analytic to pragmatic philosophy is still inspirational.
    – Dcleve
    Feb 13, 2023 at 6:12

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