Kipper's Bombshell

In a recent post (and an article I am working on), I arrived at the view that if a proposition can be known to be necessary (i.e. necessarily true or false) then either it or its negation is in the deductive closure of a set of true propositions with a priori necessary character - i.e. propositions which are such that it can be known a priori that they are necessary.

There is a new article by Jens Kipper forthcoming in Analysis, 'On what is apriori about necessities', which seems to make serious trouble for this view (as well as its ancestors). Here is the problem in my own words:

Kipper zeroes in on the fact that with some terms, such as - plausibly - 'air' and 'water', it is not a priori whether they pick out a natural kind or not. It turns out that 'air' doesn't pick out a natural kind, and that 'water' does. Now, let 'airy' be a predicate that applies to a stuff when it exhibits the superficial characteristics that air has in our world, and similarly for 'watery'.

Kipper's bombshell is to point out that 'Air is airy' is plausibly necessary (since air doesn't have some underlying nature which makes it air - rather its being air is basically just a matter of its being airy) but 'Water is watery' is plausibly not necessary (since something with water's underlying nature, i.e. being comprised mainly of H20, could have existed in quite different conditions where it isn't watery). And it definitely seems like these things could not have been known a priori.

I have mixed feelings realising this. I was really happy with my proposed link between necessity and apriority. I still feel inclined to suppose that there is something in the idea. But I cannot deny the simplicity and insightfulness of Kipper's bombshell.

Kipper considers and casts serious doubt on a view that tries to escape the bombshell by claiming that meaning change occurs when we discover whether a term like 'air' doesn't pick out a natural kind. I am pretty sympathetic to Kipper's rebuttal of this, and am inclined to look elsewhere for a way of saving, or repairing, my link. Could I perhaps figure out a way of getting propositions which clearly do have a priori necessary character and which imply propositions like 'Air is airy'?

I will post again on this matter once I get a better view of the situation.

What is Necessity De Dicto?

I recently posted an account of necessity de dicto. The purpose of this post is to pin down exactly what this topic is. The notion in question of course looms large in contemporary analytic philosophy, but it will serve us well and keep us grounded to furnish in as clear a way as possible a basic characterization of it. In a future post, I will turn to specifying the problem or task which my account is addressed to with respect to the topic. In another future post, I will state some of my assumptions and guiding ideas.

The key source for the notion of necessity de dicto is of course Kripke's Naming and Necessity. It was there that our topic was (to the best of my knowledge) first clearly isolated and characterized. Priority aside, Kripke's characterization is not easily improved upon and has been very influential. (Regarding the notion itself, not its characterization: it is a very interesting historical question to what extent this notion was present in earlier thinking. Or to what extent similar notions were, and how they may relate to the present notion. I will make no attempt here to answer this.)

Kripke's starting-point in characterizing the notion of necessity de dicto is to remark that, while many (at the time he was speaking) seem not to differentiate between a priority and necessity, he certainly will not use 'a priori' and 'necessary' in the same way (p. 34). He then, after emphasizing that the notion of a priority is an epistemological one and mentioning some issues which might arise with that notion, gives the following characterisation of necessity:

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. (pp. 35 – 36.)

This should go a long way to giving us an acceptable grasp of the notion of necessity de dicto. Kripke also says some things about the extension of the notion which may be of further help to this end. Before proceeding to that, however, I want to tighten up Kripke's characterization in a couple of ways, as well as emphasizing and de-emphasizing certain parts of it.

For one thing, note that Kripke moves freely here between talking of 'facts about the world' as well as things which can be called true or false, as the bearers of necessity. Later, he speaks also of 'states of affairs' and 'statements'. This is fine, but I want to make it clear that the topic I am addressing in my account is the notion of necessity as it applies to things which can be called true or false: statements – or as I say, propositions. This is what I mean by 'de dicto' in 'necessity de dicto'. To be still more precise about what propositions are – for a start, whether they are or involve sentences themselves, or just their meanings – is not necessary, but see this post for an approach I favour.

(At this point I should emphasize that that is all I mean by 'de dicto' in 'necessity de dicto'. The term 'de dicto', and the contrasting term 'de re', are used in various ways in philosophy. It it especially important to realize that I count all attributions of necessity to propositions as attributions of necessity de dicto, even when those propositions are “singular propositions” about individuals – i.e., propositions attributions of necessity to which David Lewis would deploy counterpart theory to understand.)

Something I want to emphasize in Kripke's characterization is the way it cashes out necessity in terms of counterfactual scenarios – to use the language of some two-dimensional semanticists, scenarios considered as counterfactual, rather than scenarios considered as actual. This could be emphasized by calling our topic 'counterfactual necessity de dicto' or 'subjunctive necessity dicto', but I avoid this for the sake of brevity.

(You may think that this is the same as the point that necessity is not to be understood epistemologically, but I'm not so sure. For one thing, I suspect there are notions of 'could actually be the case' and 'must actually be the case' which, even if 'a priori possible' and 'a priori true' may be good expressions for them, can be cashed out non-epistemologically. (Cf. this post.) For another thing, 'Could have been' talk can also be given an epistemological reading, along the lines of 'Was epistemically possible'. In any case, emphasizing that with the notion of necessity de dicto we are dealing with scenarios considered as counterfactual, can only help to avoid misunderstanding here.)

Something I want de-emphasize in Kripke's characterization, on the other hand, is the way he classifies the notion of necessity he wants to talk about as a notion belonging to metaphysics. I do not think this is essential to grasping the notion in question: that can be done without any recourse to a notion of metaphysics. Kripke's use of a category of metaphysics here may be slightly helpful in emphasizing that necessity de dicto is not an epistemological notion, but that point can be emphasized without a notion of metaphysics. Since we can easily get by here without invoking a notion of metaphysics, I think we ought to avoid doing so. I am not going to argue the point at length here, but I suspect that invoking a notion of metaphysics may lead to some unhelpful prejudice about how the notion is best to be understood and analyzed (if it is to be analyzed) – or more to the point, how it is not to be analyzed. In particular, I worry that it may cause prejudice against accounts which crucially involve semantic considerations, by promoting a vague idea that necessity de dicto is “all about” how things are in the world, as opposed to having anything to do with language and thought.

Finally, Kripke's characterization should be supplemented with something about the sense of 'necessary' being unrestricted or very broad. To see this, consider an utterance like 'It is true that I stayed home yesterday. This couldn't have been otherwise, as I had to be there to let the electrician in.' This utterance may be true, but in that case the 'couldn't have been otherwise' part is not about necessity de dicto in the sense I am interested in – we are dealing with a contextually restricted range of ways things could have been. For instance, we are probably ignoring ways things could have been in which I stop caring about having electricity, or in which I never made the appointment with the electrician, or in which the appointment was on a different day. This supplementation of the Kripkean characterization has become customary. Witness Timothy Williamson in an interview:

Something is metaphysically necessary if it couldn’t have been otherwise, in the most unrestricted sense. (Williamson & Antonsen 2010, p. 18.)

Or Daniel Stoljar, referring to:

(…) the completely unrestricted sense of possibility that philosophers sometimes call “logical” or “metaphysical” possibility (…) (Stoljar 2006, p. 34.)

Or this terminological stipulation made by van Invagen:

Modal terms will be used in their “metaphysical” or “unrestricted” sense (…). (van Invagen 2015, p. 35.)

There is a wrinkle here, however. For some things philosophers say may seem to go against the propriety of characterizing our topic in this way. On the way of speaking I have in mind, there are necessities in the sense of our topic which are not necessary in some other sense – 'logically' or 'mathematically' or 'epistemically' for example. See, for instance, this passage in Nathan Salmon (where he is arguing that an objection made to something he has proposed – the details of which don't matter here – does not hold water):

Metaphysical modality is definitely not an unrestricted limiting case. There are more modalities in Plato’s heaven than are dreamt of in my critics’ philosophy, and some of these are even less restrictive than metaphysical modality. One less restrictive type of modality is provided by mathematical necessity and mathematical possibility. […] Another type of modality less restrictive than metaphysical modality is provided by what is sometimes called ‘logical necessity’ and ‘logical possibility,’ to be distinguished from genuinely metaphysical necessity and possibility, or necessity and possibility tout court. A proposition is logically necessary if its truth is required on logical grounds alone […]. Although there is a way things logically could be according to which I am a credit card account, there is no way things metaphysically might have been according to which I am a credit card account. (Salmon 2005, p. 136)

But notice the contrast at the end of this passage between 'could be' and 'might have been'. Salmon is concerned here with what he calls 'the confusion between the generic notion of a way for things to be and the modal notion of a way things might have been'. According to Salmon, this confusion

is very probably the primary source of the idea that metaphysical modality is the limiting case of restricted modalities, that metaphysical necessity and possibility is the unrestricted, and hence the least restricted, type of necessity and possibility. For metaphysical necessity is indeed truth in all ways things might have been (modal, not generic), and metaphysical possibility is indeed truth in at least one way things might have been (modal, not generic). (ibid, p. 136.)

So, since we are explicitly talking about ways things might have been, it seems that Salmon would have no real disagreement after all with Williamson's succinct characterization of our topic, quoted above (except perhaps for some pragmatic disagreement about what to emphasize, or how best to use language to avoid potential confusions).

In any case, one thing that should be clear is that we are not dealing with a notion where certain contextually relevant matters of fact may be held fixed, as in the electrician example above.

So much for the intensional characterization of the notion of necessity de dicto. Another thing which may help us grasp the notion is consideration of its extension – cases, and what types of cases there are. Most instructive in this way are cases lying outside the overlap of necessity and a priority. After giving his intensional characterization of the notion, Kripke goes on to say that he will be arguing that, in addition to being conceptually different, the categories of necessity and a priority are extensionally different: 'I will argue below that in fact they are not even coextensive—that necessary a posteriori truths, and probably contingent a priori truths, both exist.' (Kripke 1980, p.38.)

An aspect of the character of the notion of necessity de dicto is captured vividly in some of Kripke's intuitive appeals regarding the necessary a posteriori, in particular with the use of the phrase 'given that', and similar language. For instance, if I think some object I have encountered empirically, a, is the same object as I have encountered empirically in other situations, b, then – while I might conceivably turn out to be wrong, i.e. while it might turn out to be the case that a is distinct from b – given that a is indeed b, then a couldn't have been distinct from b; 'a = b' is necessary.

Regarding the contingent a priori, perhaps the most straightforward and instructive type of case occurs when a name is stipulated to refer to whatever object satisfies some description, where the description is of a sort where an object satisfying it could have failed to satisfy it. So if I stipulate that 'a' is to refer to the inventor of the zip (if there was an inventor of the zip), then the proposition 'a, if there is an a, invented the zip' is a priori: in virtue of the way I have set 'a' up to work, it just can't turn out empirically that a exists and yet didn't invent the zip after all. Now suppose that there is an inventor of the zip. In that case, the proposition 'a, if there is an a, invented the zip', while a priori, is contingent: someone else could have invented the zip.

We have now characterized our topic, first intensionally, by taking and modifying slightly Kripke's famous characterization, and then extensionally, by pointing to two striking types of cases. The next question we must address is 'What is the problem or task in relation to the topic, to which your account is a response?' I will concentrate on this in a future post.  

References

Kripke, Saul A. (1980). Naming and Necessity. Harvard University Press. (First published 1971.)

Williamson, Timothy & Antonsen, Paal (2010). Modality & Other Matters: An Interview with Timothy Williamson. Perspectives: International Postgraduate Journal of Philosophy 3 (1):16-29.

Salmon, Nathan U. (2005). 'The Logic of What Might Have Been' in Metaphysics, Mathematics, and Meaning. Oxford University Press. Article originally published in 1989.

Stoljar, Daniel (2006). Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness. Oxford: Oxford University Press.

van Invagen, Peter (2015). 'Nothing is Impossible' in God, Truth, and other Enigmas, Szatkowski, Miroslaw (ed.),. De Gruyter.

Deduction and the Necessary A Posteriori

Consider: There is a cat here, therefore there is an animal here.

Assuming we want to say that this inference is valid in some sense, here are three things we might say about it:

1) It is an elliptical argument, involving an unarticulated premise, namely that cats are animals.

2) It is an enthymematic or gappy argument, involving unarticulated reasoning.

3) It is a complete argument in itself - neither (1) nor (2) is the case.

On the first approach, the deduction is clearly a priori. But this is not the only possible attitude. While the belief that cats are animals could conceivably be overturned by experience, it is arguably not a contingent fact that all the cats around are animals (cf. Kripke 1980). So rather than regarding this as part of the matter being reasoned from, we might regard it as part of the deductive apparatus.

Thus, on the second interpretation, we might regard the move from 'cat' to 'animal' as being licensed by an unarticulated principle of reasoning (which may be expressed in the form of an inference rule, or an axiom such as 'All cats are animals'). Or we might resist even this, and say that nothing is unarticulated - perhaps still allowing that the argument can be justified by the principles of reasoning which are held to be unarticulated on the second interpretation.

Note how natural these latter two approaches are; there does seem to be some sense in which the conclusion follows from the single articulated premise. Note also that the argument by itself satisfies the natural (admittedly problematic) modal characterization of validity, if we take the relevant modality to be subjunctive or metaphysical modality ("what could have been the case") rather than a priori possibility or epistemic modality ("what could be the case"): it could not have been the case that there was a cat here yesterday but no animal here yesterday.

This may suggest that, according to some intuitive and central concept of deduction, some facts about what can be deduced from what are empirical (i.e. not knowable a priori).

However, this flies rather completely in the face of previous philosophical thinking about deduction. It also raises the following puzzle: on one way of thinking about necessity, our holding it to be necessary that all cats are animals means that we have made a certain kind of connection between our cat-concept and our animal-concept (an empirically defeasible connection, held constant when describing counterfactual scenarios). But it is natural to think of this conceptual connection as partly constitutive of the content of thoughts involving these concepts - thoughts such as 'There is a cat here' and 'There is an animal here'. Thus, someone who doesn't have such a connection arguably isn't in a position to have those two thoughts at all: there would appear to be little room for them to have those exact thoughts and yet not be able to work out a priori that one implies the other.

My suggestion is that, when faced with this sort of puzzle, one should try to distinguish different ways of individuating content, some more fine-grained than others. When talking about thoughts in, e.g., the context of communication, a relatively course-grained individuation scheme is often most appropriate. When talking about the epistemology of deduction - and not just the epistemology - a more fine-grained approach is called for. (That is, an approach where what are for many purposes two instances of the same thought get treated as distinct structures.)

Insofar as this is right, the more general moral is perhaps something like: when doing philosophy, be willing to put multiple modes of content-individuation on the table - don't let one obsess you to the exclusion of all others.

Tristan Haze

Reference

Saul A. Kripke (1980). Naming and Necessity. Harvard University Press.

Sketch of a Way of Thinking about Modality - Part 1

[This is old and my thinking on the subject has changed quite a bit (for the better I'm pretty sure). It may be of historical interest, or interesting if you're interested in how my ideas have developed. See my more recent 'Necessity as an Attribute of Propositions' - 22/10/15]

[UPDATE: This sketch, except for parts of part 2, will soon be made mostly redundant by a paper I am working on. I expect to make a draft of this paper available in early November. A link will appear here. - TH 13/10/2011]

[UPDATE 2: The paper mentioned above is here.]

[UPDATE 3, March 2013: What appears below has been left so far behind that I'm almost embarrassed about it. For my latest on these topics, see An Account of Subjunctive Necessity.]

This is the first installment of a two-part series of posts where I aim to sketch some ideas about modality which will feature in a book I am working on, Necessity and Conceptual Systems. The material is still very much under development, and I apologize for the obscurities which the reader will inevitably find in it. Comments and criticisms are very welcome.

In this first part, I will introduce the approach, and indicate how it handles the necessary a posteriori, using 'Hesperus is Phosphorus' as a case-study. In part 2 I will discuss the notion of de re modality, of essence, and natural-kind examples such as 'Water is H20', as well as some more general issues which arise on my approach (especially to do with epistemic modality and ascriptions of intentional content).

In the Golden Age of analytic philosophy, necessarily true propositions were widely taken to be those which are satisfied by (or 'come out true' on) all configurations of some conceptual or linguistic system. Possibility was understood in terms of satisfaction by at least one configuration. Our conceptual system, our means of understanding the world, is here thought of as something like a model, or a machine, which has moving parts, and which can be put into various positions or configurations. Each configuration can be thought of as corresponding to, or satisfying, or even being, a set of propositions. (I have taken many liberties in the formulation of this description.)

Conceptual or linguistic systems of the kind in question were thought to be describable with "semantical rules" for a language, and necessary propositions were thus commonly taken to be a priori and true "in virtue of the meaning" of the terms involved (cf. Carnap's Meaning and Necessity, Ayer's Language, Truth and Logic). This yields a notion of necessity reminiscent of the notion of truth-functional tautologousness. (Earlier, in the Tractatus - which was a major inspiration to both Ayer and Carnap - this relationship is much closer than mere reminiscence.)

This sort of view was attacked by Quine in at least two ways (cf. his 'Truth by Convention', 'Two Dogmas of Empiricism'). Quine's undifferentiated picture of language had a sobering or worrying effect, but it did not stop people carrying on with some version of the view in question. This is connected with the fact that it amounted to a kind of quietism or abstinence with respect to the relevant sorts of notions (semantic, modal), rather than a sustained attempt to attain positive insight about them.

The really decisive blow to the Golden Age view of modality came from Kripke. His fundamental contribution was to persuasively argue that the a priori does not coincide with the (metaphysically) necessary, and relatedly, that epistemic modality ("what could be the case") is to be distinguished from metaphysical modality ("what could have been the case" in a certain unrestricted sense). This contribution was closely bound up with Kripke's ideas concerning naming and reference, more on which in a moment. The recognition of the necessary a posteriori in particular, and the associated idea that conceivability doesn't entail possibility, has led to a reaction against views of modality of the Golden Age sort.

(About 'metaphysical modality': one sometimes hears it said of a philosopher that they countenance metaphysical modality, as though this indicates that the person holds some sort of doctrine, which may be quite esoteric. But 'metaphysical modality' is just a label for me - synonymous with 'subjunctive modality' - for a notion "detected" in the logic of language. That said, someone who felt this notion was, e.g., a trivial artifact of the way we happen to talk, rather than a deep artifact of the way we think, would probably not want to use this label.)

My approach to modality retains the view that necessity - metaphysical necessity - can be fruitfully understood in terms of invariance through all configurations of a conceptual system. But it also takes Kripke's separation of the a priori and the metaphysically necessary fully to heart. This latter point is one respect in which my approach differs from that of the two-dimensional semanticists. Another key contrast is that the possible worlds framework is not fundamental to my view.

Broadly speaking, I handle the necessary a posteriori by doing two things. Firstly, I work with a much more fine-grained notion of 'conceptual system' than did the logical empiricists. (The sense of 'fine-grained' here should become clearer in a moment.) Secondly, I embrace a certain kind of semantic externalism - roughly, the view that sense doesn't determine reference (other ways to put this which for me are roughly equivalent: intension doesn't determine extension, concept doesn't determine object).

I will illustrate how this works with respect to a classic example of the necessary a posteriori: 'Hesperus is Phosphorus'.¹

I follow Kripke in holding that proper names do not have reference-determining senses (which hangs together with semantic externalism via Putnam's idea of Twin Earth), and also that proper names do not have a semantics which can be given in the form of general conceptual content such as definite descriptions, or clusters thereof (irrespective of whether this content can be said to determine reference).

I do not, however, accept the (to my mind very strange and confused) idea that proper names are 'mere tags' (Ruth Barcan Marcus's phrase), that all there is to the meaning of a name is its referent, etc. This idea is sometimes associated with Mill's claim that names have no 'connotation', only 'denotation', and also with the phrase 'direct reference'.²

We have individual concepts - concepts of individuals, of particular objects - and we often associate these with proper names. This sheds light on Kripke's rigid designation thesis (the thesis that a referring proper name designates the same object in all possible worlds at which that object exists). If names are associated with individual concepts - concepts of particular objects - then it is immediate that they will designate the same object in all possible worlds where that object exists; designating another object is out of the question, since we are holding fixed the associated individual concept. We may thus distinguish rigid designators such as ordinary proper names, which designate rigidly because they are directly associated with individual concepts, from other rigid designators such as definite descriptions in mathematics.

Once we recognize individual concepts in this way, we can say that when someone accepts that Hesperus is Phosphorus (having previously taken them to be distinct), there is a change in their conceptual system - in the relevant fine-grained sense. Of course, in a more coarse-grained (and more ordinary) sense, we can say that they have before and after the same conceptual system. The fine-grained change consists in the unification of two individual concepts. The original concepts, we might say, are not blended irrevocably but remain as aspect-concepts united under a common master. From now on, it should be kept in mind that conceptual systems will usually be individuated here in this fine-grained sense.

In the former conceptual system (call this 'the Babylonian system'), where the Hesperus-concept is separated from the Phosphorus-concept, the distinctness of Hesperus and Phosphorus is invariant through all configurations of the system; if one positively believes that Hesperus and Phosphorus are distinct, one will say that, although it might conceivably turn out that Hesperus is Phosphorus after all, given that it isn't, Hesperus could not have been Phosphorus. (And one will of course be wrong.) In the latter conceptual system (call this 'our system'), where the Hesperus- and Phosphorus-concepts are unified, the identity of Hesperus and Phosphorus is invariant through all configurations of the system; when one knows that Hesperus is Phosphorus, one will say that, although it might conceivably turn out that Hesperus is distinct from Phosphorus after all, given that it isn't, Hesperus could not have been other than Phosphorus.

Now, with our fine-grained understanding of conceptual systems in place, I maintain that we can still say that all (metaphysically) necessarily true propositions are satisfied by all configurations of their host conceptual systems. We can even say that a truth is metaphysically necessary iff it is satisfied by all configurations of its host system. We just can't say that all propositions which are satisfied by all configuration of their host systems are necessary truths. So far, then, we can say what distinguishes necessary from contingent truths, but we can't say what distinguishes necessary truths from other proposition which are satisfied by all configurations of their host systems - we might call these 'false propositions of necessary character'. What can we say that will do this?

I think we can say something like: a proposition P is necessarily true iff it is satisfied by all configurations of its host system and the concepts involved in P are jointly adequate to their objects with respect to P.

First I want to say that I am not concerned to provide a reductive analysis of modal concepts. Relatedly, I am happy for the relevant modal notions and my ternary relation of 'adequacy' to be explanatory of each other; I do not suppose it is a one-way street, where my notion does all the explaining, nor do I take my notion to be more "fundamental" in any metaphysical sense. I am interested in showing (and making) connections.

I will make a start at explicating the above proposal by indicating how it applies to the 'Hesperus is Phosphorus' case. In the Babylonian system, the Hesperus-concept and the Phosphorus-concept are not unified (are taken to represent distinct objects), but they both have the same object, the same extension, and so together (jointly) they are inadequate to their objects with respect to 'Hesperus is not Phosphorus'. So their proposition 'Hesperus is not Phosphorus' fulfills the first condition given above, before the 'and' - it is satisfied by all configurations of their system - but it does not fulfill the second. Our Hesperus- and Phosphorus-concepts, which also have the same extension, are in contrast united, as aspect-concepts, under a common master concept (the concept of Venus). Hence they are adequate to their objects - or object - with respect to our proposition 'Hesperus is Phosphorus'.

Why do I not simply say that a proposition is necessarily true iff it is satisfied by all configurations of its host system and its concepts are jointly adequate to their objects? Why do I add 'with respect to that proposition'? I will explain this with an example. Assume for the sake of argument that Hesperus (Venus) is necessarily not intelligent - i.e. that Hesperus could not have been intelligent. Now, suppose someone believes that Hesperus is intelligent, and necessarily so - loosely speaking, that it is part of their concept of Hesperus that it is intelligent. In that case, their concept of Hesperus would not be adequate to its object with respect to 'Hesperus is intelligent'. But they may know, for all that, that Hesperus is Phosphorus, and so their concepts of Hesperus and Phosphorus might be jointly adequate to their object with respect to 'Hesperus is Phosphorus'.

Conversely, someone may know that Hesperus is necessarily not intelligent, while mistakenly believing that Hesperus is not Phosphorus, thus having an adequate conceptual situation with respect to propositions about the intelligence of Hesperus, but not with respect to propositions about the identity of Hesperus and Phosphorus.

Speaking broadly, necessity is, on this understanding, not simply a matter of a proposition having a certain status in a conceptual system. It is, as well as that, a matter of the system being adequate to its objects with respect to that proposition. The adequacy of some set of concepts to their objects obviously depends on the identity (and nature) of those objects - and this is not in general determined by the system. (This is how semantic externalism fits in.) Hence you cannot, in general, tell simply by looking at a proposition in a system whether or not it is necessarily true - there are a posteriori necessities.


The compatibility of externalism with rigid designation
(Postscript added 14 August, 2011.)

It may look as though there is a tension between my externalist claim that the extension of an individual concept is not in general determined by the concept itself, and the claim that names rigidly designate: if names are tied to individual concepts, and individual concepts do not in general determine their extension, it looks like a given individual concept can have different extensions in different environments. This is so (at least, when we individuate concepts internally) but there is no real tension here: the rigidity applies to names in use - names tied to token individual concepts embedded in an environment. Individual concepts are not like general concepts: the whole point of them is to apply to one particular object. And so the contrast between names and definite descriptions remains: when we consider counterfactual scenarios and hold the meaning of our terms fixed, our names which are tied to individual concepts always refer to 'the same object'.

This is all perfectly compatible with the fact that the same concept, in a different environment, might be connected up to a different object. The extension of our individual concepts may in some cases even change over time: if an object we know is replaced with a substitute, and we don't notice, after a while it will become true to say that our individual concept has changed its extension. But we don't let the extension change "across possible worlds" when representing counterfactual scenarios using a particular individual concept in a particular environment.

Part 2.

Individual concepts are under-discussed in contemporary philosophy. For further online reading on what they can do, see:

- My post at Philosophy, et cetera, 'An advertisement for individual concepts'

- A recent article by linguist Barbara Abbott, 'Support for Individual Concepts'.

- John McCarthy's article, 'First Order Theories of Individual Concepts and Propositions'. (Warning: arguably contains some use-mention confusion.)

Interestingly, neither of these authors are (primarily) philosophers.

1 I pass over one well-known issue here, to do with the fact that Hesperus/Phosphorus might not have existed. There is a discussion of this on Greg Frost-Arnold's blog. If one is really worried about this, consider instead the example 'If Hesperus exists, then Hesperus is Phosphorus'.

2 It should be noted, however, that Mill's claim is appropriate if 'connotation' is interpreted to mean 'reference-determining sense' or 'general conceptual content', and likewise that the phrase 'direct reference' is appropriate if 'direct' is interpreted to mean 'not via general conceptual content' or 'not via reference-determining sense'.