Abstract
The paper sketches an epistemology of de re possibility (for concrete entities) centred on the notion of similarity. The proposal is, roughly, that we know about some entities’ unrealized possibilities by extrapolation from knowledge about some other, similar entities’ realized possibilities. The account is limited, among other things, in that it does not cover knowledge of de re necessities or essentialist knowledge, if we have it. But even if alternative epistemologies could explain that type of knowledge too, the current account is found to best explain the de re possibility knowledge, thereby resisting a potential charge of redundancy.
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Notes
- 1.
A salient exception here is (Williamson 2007).
- 2.
The idea is that a posteriori necessities like, perhaps, that Socrates is necessarily human, can be factored out into an essentialist principle—supposedly (purely) a priori—, like all humans are necessarily human, and an a posteriori non-modal truth, like Socrates is human. For more on how a posteriori necessities can be subsumed under a rationalist programme, by claiming them to be fundamentally a priori, see for instance (Peacocke 1999: 168–9).
- 3.
- 4.
This growing non-rationalist tendency has several instances in the literature. Salient pieces include (though the list is not exhausted by): (Biggs 2011); (Elder 2005); (Fischer 2015, 2017); (Hanrahan 2007); (Hawke 2017); (Jenkins 2010); (Leon 2017); (Nolan 2017); (Rasmussen 2014); (Roca-Royes 2007), (Strohminger 2015); (Tahko 2017); (Williamson 2007).
- 5.
Although I myself have done that in the past (Roca-Royes 2010), it would be naïve to capture this idea with a biconditional along these lines: “For any entity e and property P, Possibly-P(e) iff P(e) is compatible with e’s essential facts”. This is unnecessarily strong. Assume that the laws of nature are necessary. It might still be compatible with all of e’s essential facts that e inhabits a world with different natural laws. That would then be possible according to the bi-conditional but impossible by assumption. It might also be compatible with all of e’s essential facts that e inhabits a world where the Eiffel Tower is made of wood. This shows that the rough idea must be captured by a somehow weaker statement (e.g., by applying some convenient restriction on the relevant P’s; by not restricting the right-hand side of the biconditional to e’s essential facts, involving instead all essential facts; or somehow else). For current purposes, the rough idea should suffice.
- 6.
The qualification that makes me add ‘largely’ is this: it would be independent of knowledge of unrealized de re possibilities.
- 7.
This is the recommendation to avoid theories of modal knowledge that, like Peacocke’s (1999) or Hale’s (2013) explicitly do, take the ontological priority of essence over modality as suggesting a corresponding epistemological priority too: “According to the essentialist theory, metaphysical necessities have their source in the natures of things, and metaphysical possibilities are those left open by the natures of things. Although the theory does not, in and of itself, say anything about how we may come to know what is metaphysically necessary or possible, it seems to me that it strongly suggests a particular approach to modal knowledge. […] one might expect an essentialist explanation of modal knowledge to follow a necessity-first approach.” (Hale 2013, 253–4)
- 8.
Disagreement as to whether Gandhi is essentially human easily translates into disagreement as to whether he could be, for instance, a cat.
- 9.
Hale’s (2013), for instance, is a nice attempt at elucidating essentialist knowledge—to me, with a reductionist flavour—much in need of serious scrutiny. A different issue is whether success in elucidating essentialist knowledge could help the project of defending an essence-based epistemology; I offer reasons for pessimism in Sect. 12.5.
- 10.
- 11.
These grounds exclude more recent accounts of pieces of essentialist knowledge like Hale’s (2013) and Bigg’s (2011). Were we, after adequate examination, to be in a position to draw analogous conclusions, the grounds would be strengthened. I cannot offer a treatment of their views here and, as a result, I shall only rely on the moderate grounds mentioned in the main text. Something that can be noted briefly, however, is the following: even if accounts like (Hale 2013) and (Biggs 2011) were successful in explaining the essentialist knowledge they focus on—i.e., even if successful as far as their running examples are concerned—, for their accounts to serve an essence-based strategy, their explanations would need to be sufficiently generalizable so as to support at least a moderate necessity-first account. (‘Moderate’ in the sense of Hale (2013, 253).) That is a necessary condition that remains to be seen met. But even if it was met, I do not think it is sufficient. In the concluding remarks (Sect. 12.5), I briefly explain why an essence-based epistemology is unlikely to be correct irrespective of the success of an explanation of essentialist knowledge.
- 12.
For it is also in part a reaction to my dissatisfaction with accounts which, like Williamson’s, resist the label ‘rationalist’ while not, after scrutiny, that of ‘essence-based’.
- 13.
This does not commit me to agreeing with van Inwagen on where the dividing line lies. I actually think that we have not been told enough, in his foundational ‘Modal Epistemology’ (1998), about what van Inwagen thinks on the matter, but this is no impediment to recognizing that the distinction is an important one and the phenomenon being tracked likely a real one.
- 14.
To qualify: About spatio-temporally located entities that are also spatio-temporally unified and spatio-temporally related to us.
- 15.
The notion of expired possibility is to be understood as capturing metaphysical possibilities whose actualization has been ruled out by the actualization of another possibility metaphysically incompossible with the first. For instance, John Kennedy’s possibility of dying of a heart attack expired the moment he died shot. This is not to say that dying of a heart attack ceases to being a possibility for Kennedy; it remains true that Kennedy could die (have died) of a heart attack.
- 16.
I believe that the case should be treated the same whether the diamond there is interpreted as nomic or as metaphysical necessity. So I am not suggesting that we go from actuality to nomic possibility and from here to metaphysical possibility. (For reasons I cannot extend on here, I believe that route is faulty.) Rather, we go from actuality directly to metaphysical possibility (or any other alethic modality). We have, at bottom, a family of principles of the same form. I’m grateful to Margot Strohminger and Barbara Vetter for pressing me on this.
- 17.
- 18.
I am adding ‘the beginning of’ because the φ-facts will (typically) be themselves temporally extended facts and might on occasions overlap with ψ(a) at a later stage.
- 19.
It is to be expected that, more often than not, the possibility of ψ-ing will be epistemically accessible by means of two or more different principles involving (slightly?) different φ’s in their antecedents. (For instance, as motivated in Sect. 12.3, the different principles might involve a more and a less determinate property.) This does not conflict with the existence of an epistemic priority of the sort described above, but it requires me to refine/qualify the claim as follows: there must be some φi such that knowledge that φi(x) grounds the transition to the possibility knowledge.
- 20.
Alternatively, the principle could be akin to “\( \upvarphi \left(\mathrm{x}\right)\to \diamond \mathrm{O}\left(\mathrm{x}\mathrm{b}\mathrm{c}\right) \)”. As what follows in the main text will make clear, nothing essential depends on it.
- 21.
Nothing essential depends (either) on the fact that I am constructing this class as containing pairs instead of triples. I am doing so for vividness.
- 22.
If nomic knowledge allows us to know too that unhealthy sperms and egg cells are only contingently unhealthy, then, we could delete the bracketed qualifications ‘healthy’ in the main text. I am adding them out of cautiousness and biological ignorance.
- 23.
Here is a far-fetched scenario reflection on which has clarificatory value. Suppose we had experiences of human beings metamorphosing into cats, into dogs, of dogs into cats, into humans, etc. There is a (reasonable) question here as to whether we would be in front of human beings, cats, dogs, etc., but this issue is inessential to the point I want to make and might distract us away from it. So let me rephrase the supposition in a way that blocks that question: suppose that we had experiences of human* beings metamorphosing into cats*, dogs*, etc. In such scenario, being a human* being would be apt for the epistemic role that qualitative anchors are said to play: knowledge that Gandhi is a human* being would enable us, together with a (would-be) principle that human* beings can metamorphose into cats*, to transition to knowledge that he can be a cat*. However, for all we know—i.e., with our current/actual state of knowledge—about human beings (and cats, and dogs, etc.), the property of being human does not meet the conditions for being (i.e., for acting as) a qualitative anchor. (See the third comment in Sect. 12.4.1 for more about the implications of the notion of qualitative anchor being an epistemic notion.)
- 24.
One might for instance submit that the absence of empirical evidence in favor of (v) and (vi) should constitute abductive grounds against them. Whether such use of abduction is epistemically adequate deserves exploration. I am inclined to think that when the absence of empirical evidence is due to its impossibility (as in the current cases) the epistemic adequacy of such uses of abduction are dubious. This, perhaps, explains the lack of persuasiveness of abductive arguments that have this feature.
- 25.
Perennial properties are properties that satisfy the principle that once acquired, never lost.
- 26.
There are various reasons, varied in nature, that advise against directly testing a hypothesis like hearted animals can die of a heart attack. Yet, the actual world provides (has provided) enough known cases of people dying of heart attacks for such knowledge to ground the judgment that the hypothesis that hearted animals can die of heart attacks has been sufficiently (indirectly) corroborated.
- 27.
When dealing with claims (v) and (vi) we were able to establish more than the mere absence of qualitative anchors; namely, their impossibility in those cases. To recall the reason: There could be no φ such that, in virtue of knowing Malala to be φ she can be known to be able to subsequently originate from b and c. I don’t think that their impossibility is salient to mark the difference I wish to mark here in relation to other expired possibilities. I believe it to be relevant, however, (as briefly suggested in footnote 22), when it comes to scrutinizing the idea that the absence of inductive and empirical evidence for claims like (v) and (vi) provides, in these circumstances, no abductive grounds against them.
- 28.
De dicto necessities require a different treatment altogether.
- 29.
This relies on the intuition that also supports the uncontroversial Converse Barcan Formula: \( \exists \mathrm{x}\diamond \upvarphi \left(\mathrm{x}\right)\to \diamond \exists \mathrm{x}\upvarphi \left(\mathrm{x}\right) \).
- 30.
This need not be so with the perhaps-limitations of the current knowability model. As just recapitulated in the main text, I suggested in Sect. 12.3 that our confidence across modal judgments varies: I have no doubt that Messy can break, but I’m less confident, though tend to believe, that there could be naturally purple cows. I tend to believe so because, even if scarce, there are some naturally purple animals; I am less confident because they are all genetically quite distant from cows. Perhaps the justification that I get, for the possibility of purple cows, from the existence of those other purple animals is insufficient to turn my modal judgment into a piece of knowledge (even if it is/were true). If insufficient, I do not know (at least not by those inductive means) that there could be naturally purple cows. If I do not know it by these means, then, the current model does not (consequently) explain how do I know it. This would then be another limitation of the account. This type of limitation, however, differs from the ones dealt with in Sect. 12.4 in that, in these cases but not those, we cannot rule out that time—more accurately: future evidence—will change our epistemic situation with respect to them.
- 31.
It does constitute grounds against some (rarely endorsed) essentialist claims. For, our de re possibility knowledge puts us in a very good position to obtain partial knowledge of essences. If I know that I can break any of my arms, I am thereby in a position to know that, whatever my essence is, it does not preclude the breaking of my arms. So, although I have never broken any of them, I know it is not essential to me not to have broken arms.
- 32.
- 33.
The persuasiveness of this reasoning is not diachronic. The fact that there is a time when the asymmetry holds is sufficient for the argument to retain its persuasiveness even if, eventually, our degree of confidence in essential matters manages to match that in ordinary matters.
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Acknowledgements
Earlier drafts of this paper were presented in Aarhus, Belgrade, L’Aquila, Lisbon, London, Mainz, Paris, Stirling and York. I am grateful to the audiences on all those occasions for stimulating discussions. Special thanks are due to Ralf Busse, Guislain Guigon, Bob Hale, Christian Nimtz, Duško Prelević, Pierre Saint-Germier, Silvère Schutkowski, Margot Strohminger, Anand Vaidya, Barbara Vetter, and Tim Williamson. I am also greatly thankful to the editors of this volume, Bob Fischer and Felipe Leon, for their careful reading of, and helpful suggestions on, the submitted version. This paper was written with support from the RCUK for an AHRC Leadership Fellowship project with the title ‘Towards a non-uniform epistemology of modality’.
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Roca-Royes, S. (2017). Similarity and Possibility: An Epistemology of de re Possibility for Concrete Entities. In: Fischer, B., Leon, F. (eds) Modal Epistemology After Rationalism. Synthese Library, vol 378. Springer, Cham. https://doi.org/10.1007/978-3-319-44309-6_12
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