Metaphysical Necessity Reexamined

Metaphysical Necessity Reexamined

When Kripke introduced the phrase “metaphysical necessity” in Naming and Necessity he didn’t say much about the nature of this type of necessity beyond distinguishing it from the a priori and so-called epistemic necessity. These are his words: “The second concept which is in question is that of necessity. Sometimes this is used in an epistemological way and might then just mean a priori. And of course, sometimes it is used in a physical way when people distinguish between physical and logical necessity. But what I am concerned with here is a notion which is not a notion of epistemology but of metaphysics, in some (I hope) nonpejorative sense. We ask whether something might have been true, or might have been false. Well, if something is false, it’s obviously not necessarily true. If it is true, might it have been otherwise? Is it possible that, in this respect, the world should have been different from the way it is? If the answer is ‘no’, then this fact about the world is a necessary one. If the answer is ‘yes’, then this fact about the world is a contingent one. This in and of itself has nothing to do with anyone’s knowledge of anything…[We] are dealing with two different domains, two different areas, the epistemological and the metaphysical”. (35-6) Later he cites various examples of metaphysical necessity, which have become well known: necessity of identity, necessity of origin, necessity of natural kind, necessity of constitution. What he doesn’t do (here or subsequently) is engage in an attempt to analyze or articulate what this kind of necessity involves. He leaves it at an intuitive (his word) level without attempting a systematic taxonomy or elucidating exactly what such necessity amounts to—its general principles, its metaphysical implications, its epistemology, its problems and puzzles. We know it is not the same as certainty, or the a priori, or analytic truth; but what is it exactly—what is its nature, its analysis? What makes it what it is? I think, in fact, that we have a very shallow and rudimentary understanding of it, though it is entirely real. It belongs to the natural world independent of the human mind, or any mind: it is among the facts of the world (as Kripke intimates) along with shape, size, number, etc. We have the ability to know its distribution, though howwe know this is obscure. Some properties are essential and some are accidental and we can tell which is which, and this is baked into reality (into any reality). But beyond that we draw a blank. When God created reality and installed necessity into it, what did he do exactly? How did he decide what to make necessary and what contingent, and how did he implement his plan? What is the structure of a modal fact? How does modality arise? Is it emergent or primitive? How are the different kinds of necessary truth related? First, we must settle on a rough taxonomy. In addition to the four types mentioned by Kripke, I will add necessities of shape: generally speaking, particular objects necessarily have the shape they actually have. You cannot drastically alter the shape of an object and expect it to retain its identity—say, a statue, or a mountain, or a computer.[1] If you change the form sufficiently, you destroy the object—say, by melting it down or rearranging its parts. The object will not continue to exist just by virtue of its previous parts still existing (its molecules, its elementary particles). Shape contrasts with color: changing the color of an object never destroys its identity—color is accidental, contingent.  The geometry of an object is integral to its identity, but the color of an object is not. So, now we can ask how these various types of necessity relate to each other: are some more basic, or more general, or more evident? It seems to me that the necessity of identity is the most general for the simple reason that everything is necessarily self-identical (including numbers and mental states) but not everything has an origin or a species or a composition or a shape. A harder question is what unites the various cases: what do they all have in common such that they are cases of essence? Evidently, each case is sui generis, so we can’t hope to reduce all cases to a single type; there really are quite distinct types of metaphysical necessity (de re necessity). Five types, to be exact: five different sorts of metaphysically necessary fact. But what unites them? Nothing, it seems; yet they all qualify. Nor is this a matter of family resemblance. Yet we have a well-defined class of de re necessities. If we ask what makes them all necessary, we draw a blank. This renders metaphysical necessity different from epistemic necessity and analytic necessity: the former are all cases of certainty, the latter cases of meaning inclusion (“conceptual containment”). Here then is our first puzzle: we don’t know what unites the class of metaphysical necessities (or metaphysical contingencies). It seems like a motley crew. It seems, in fact, arbitrary, unprincipled, a ragbag. Second, presumably the modal status of a property is a function of that property: it is built into essential properties that they are essential, and similarly for contingent properties. It is part of the essence of shape (say) that shape is an essential property, and it is part of the essence of color that color is not an essential property. These things are in the nature of the properties in question—what those properties intrinsically are. But what is this building in? Is it that some properties just can’t help being essential, while others are condemned to being merely accidental? And how do you build in this kind of status? It’s not as if properties have a genetic code or a slot for their modal status! How do shape properties differ from color properties qua properties: what is their inner architecture like? Would it be logically possible to invert their modal status by exchanging the modal type? So, we don’t know the nature of properties such that some are essential and some accidental—which means we don’t know the nature of properties. Thus, we don’t know the nature of facts: how facts are constructed, how they break down. Third, and more positively, there exists a kind of natural pairing of essential properties and contingent properties: for every essential property there is a contrasting contingent property, so that one naturally suggests the other. Thus: shape contrasts with color; origin contrasts with career or history; species contrasts with reproductive success or geographical distribution; constitution contrasts with spatial location; identity contrasts with parthood (i.e., things are necessarily self-identical but their parts can be replaced). When you are explaining the necessary-contingent distinction to someone you always find yourself citing something from the contrast class in order to get the concepts across: what is necessary is what is not contingent, what is contingent is what is not necessary. Essential properties are accompanied by contingent properties that contrast with them. In fact, we can say that every particular instantiates both essential and contingent properties: nothing instantiates only essential properties or only contingent properties. And this is a necessary truth: it is as if one needs the other. It is how the world is fundamentally structured: the necessary side by side with the contingent, necessarily. Fifth, there is nothing in between—nothing that is neither necessary nor contingent but somewhat necessary or partially contingent. This is a strict dichotomy; you are either one or the other. Sixth, we have a remarkable talent for telling which is which: we don’t generally have any difficulty deciding whether a property is necessary or contingent. The metaphysical distinction is easily translated to an epistemological distinguishing: it is as if we have a priori insight into the modal category of a property, vouchsafed by our concepts. We just see that origin is essential and career inessential. We have fine-tuned modal intuitions (better than our moral intuitions, which tend to be more labored). Still, this epistemic facility is not accompanied by metaphysical insight into the nature and workings of de re necessity; of that we are at a primitive level. We don’t even know what it is about a property that makes it necessary or contingent.[2]

Colin McGinn

[1] How much tolerance for shape alteration an object has is not easy to say. Clearly, small alterations are consistent with identity preservation, while massive alterations of shape are not. It may vary from one type of object to another: you can’t alter a mouse much, inside and out, before you lose the individual (say by giving it the shape of a mole), but clouds seem more tolerant of shape transformation. Some things change shape naturally, while others do not. This is why we are unsure whether a butterfly larva survives metamorphosis.

[2] Is it the same thing that makes all essential properties essential or could it be different things in different cases? Do all properties have their modal status built into them at birth, so to speak, are could it be acquired? Did God have to add anything to properties once he had created them in order to render them necessary or contingent? Is it supervenient on the property itself or is it injected from outside? Do these questions make sense or do they arise from mistaken analogies. The whole subject seems impossibly obscure.

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4 replies
  1. Robert Stoothoff
    Robert Stoothoff says:

    Apropos your question “How do shape properties differ from color properties qua properties…?”, here is an answer which I offered in my contribution to an Aristotelian Society Joint Session symposium ‘What Actually Exists’ in 1968. The shape of a (physical) object is an actual property of the object, whereas its colour is not an actual property of it, because a change in the object’s shape implies a change in the object itself, whereas a change in the object’s colour does not imply a change in the object itself. It is precisely this fact – that the object has an actual property (a property a change in which implies a change in the object) – that makes the object an actual object. Needless to say, this explanation needs some tidying up.

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  2. Robert H. Stoothoff
    Robert H. Stoothoff says:

    I prefer “actual” over ‘intrinsic” or “essential” because this puts the concept of change in the foreground, unlike the other terms, which are shrouded in centuries of metaphysical mist. Of course the concept of change raises metaphysical issues, but I believe these are more tractable than issues concerning the concepts of intrinsic and essential properties.

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