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!

  • As a starting point, you can see Varieties of Modality as well as The Epistemology of Modality. Feb 15 '19 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 '19 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 '19 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 '19 at 14:24

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.

  • 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 '19 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 '19 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 '19 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 '19 at 14:08
  • I couldn't find anything on necessity specifically in the original Two Dogmas, but in Two Dogmas in Retrospect he writes "It is simply in this, I hold, that the necessity of mathematics lies: our determination to make revisions elsewhere instead. I make no deeper sense of necessity anywhere. Metaphysical necessity has no place in my naturalistic view of things, and analyticity hasn't much." In Pursuit of Truth he says "we write 'necessarily' to identify something that follows from generalities already expounded..." Carnap is the one who linked analyticity to necessity.
    – Conifold
    Feb 18 '19 at 5:02

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