Sunday 1 November 2015

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 bgiven 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.  


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.

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