Martin(1) felt the need to theorise about absences in order to provide truth-makers for negative existential truths such as, ‘There are no arctic penguins.’ No aggregation of things, properties, relations and (positive) facts is sufficient alone to rule out that there are penguins in the arctic. It is the absence of penguins that clenches it. Yet, Martin claims that these absences are not entities. They are localised states of the world or universe.(2) Similarly, Kukso says that absences are features of the physical world, located in space and time.(3) Apart from the thought that one man’s localised state or feature of the universe is another man’s entity, there is a more focused concern about this non-entity position. We might consider Martin’s quite reasonable claim that absences are always absences of something – some entity or entities.(4) Kukso agrees with this claim.(5) If this claim is correct then we have a criterion of identity for absences: the identity of an absence will be determined by the identity of that of which it is an absence and its spatio-temporal location. A criterion of identity may not be a necessary condition for thing-hood, but surely it is a sufficient condition.
Martin and Kukso also take it as a virtue that their absences are located in space and time because such location is a mark of the concrete and the avoidance of abstracta has the odour of respectability for a metaphysics that sits comfortably with a naturalistic methodology. Yet, the claim that absences have a location may well confuse the properties of the absence with the properties of that of which it is an absence. If the absence of liquid in a cup does not have the property of liquidity, how can it be assumed that it has the relational property of being in the cup? A principled basis is required determined that some properties of an absent thing are shared with its absence, and no such principled basis is available to privilege as such shared properties relational location properties. There is no reason to prefer the view that the absence of Pierre is located in the café as against the view that some absence is the absence of the state of affairs Pierre-in-Café X. Martin and Kukso gratuitously privilege the sharing of relational location properties because that is what their methodology requires. It is not at all clear from intuitions of absences that this sharing is essential to them. Indeed, the opposite view will be given preference below. That is, the criterion of identity for absences is simply the identity of those things of which they are absences.
The Lewis’ initiated the recent discourse on holes within Anglophone philosophy with their article of that name.(6) The respective conclusions of Argle and Bargle – the personae between which a dialogue proceeds – are that holes are material hole-linings and that holes are irreducibly immaterial entities. Another materialistic approach is to take holes to be a region of space-time, bound by a hole-lining. To be precise, as holes can be moved and spatial regions cannot, holes are a 4-dimensional region of space-time that extends along the path of “motion” of its 3-dimensional time-slices. Things may move through space, but they do not move through space-time.(7) Taking up Bargle’s approach, Casati and Varzi(8) instead argue that holes are immaterial things that are ontologically dependent upon discontinuities in the surfaces of material things. To be precise, Casati and Varzi(9) argue that material things are made of space-time, but are not identical to space-time. That is, material things are made of qualified space-time: space-time at which certain properties are instantiated. By contrast, holes are made of (though, not identical to) unqualified regions of space-time. As material things are made of qualified space-time and holes are made of unqualified space-time, holes are immaterial things. However, this is not a view of holes as sui generis things and it may take up a merely terminological dispute as to whether holes are material or immaterial things. Sorensen(10) argues that holes are not immaterial things because materialism requires both atoms and void. That is, while holes are not constituted by matter, they are things at home in a materialist’s world. Yet, there is still the question as to whether or not holes taken as sui generis things can be eliminated or reduced to other kinds of thing for the sake of parsimony. All three of the above approaches reduce holes to space-time and/or matter in some way. Yet, each leaves out something in the nature of holes for the reduction.
First, Casati and Varzi(11) make an important point as to the nature of holes in that, in addition to having hosts (those things in which they are holes), holes can have guests, i.e. the things that partially or completely fill. Holes can be filled without ceasing to be a hole. In term of Casati and Varzi’s theory, holes taken as “immaterial” things are made of either qualified or unqualified space-time. Miller(12) notes that this inclusive account, holding that holes can occupy the same spatial region as material things, is not the only available interpretation of the filling of a hole. One might, instead, hold to an exclusive account wherein a hole cannot occupy the same spatial region as material things and, so, a filled hole ceases to be a hole. Miller(13) goes on to argue that the internal and external accounts are equally warranted for any given hole and this equivalence motivates her conventionalism about holes. That is, it is purely a matter of convention as to whether or not the contrast between the matter contained in or constituted by a given region of space-time is sufficiently diverse to be called a hole. Yet, there is a more realistic way to reconcile the distinction between internal and external accounts of holes and their fillability. We might hold that Casati and Varzi fail to distinguish between cases in which hosts are in some way completed or restored by the filling of a hole and cases in which the host is not so completed or restored. In the former cases, there ceases to be a hole, while in the latter cases there is yet a hole in the host. These two kinds of cases may be distinguished as events of filling in a hole and filling up a hole respectively. While a filled in hole is also filled up, a filled up hole is not necessarily filled in. The difference lies with the material used to fill up a hole. Rather than to say that this difference is purely a matter of convention, a realistic approach is to say that holes are a kind of absence: holes are absences of the material of their hosts. If the material used to fill a hole is not of the kind and arrangement necessary to complete or restore the host then the host will still have a hole as the relevant material will still be absent. The hole has not been filled in; it has merely been filled up. It is this distinction between the possibilities of being filled in and being filled up, realistically construed, for which theories of holes that seek to reduce them to matter and/or space-time cannot give an adequate account.
For a simple example of the contrast between filling in and filling up, we may note that Sorensen(14) considers that shadows are holes in light. As such, shadows can have guests or fillers, just as all holes do. All manner of things can be in shadow, including light that “pollutes” the shadow. Light pollution is a light filler of the wrong kind to fill in the shadow because it contrasts with the light of the hole-lining that bounds the shadow. Sorensen allows that the filler of a shadow can completely fill the shadow, so that a shadow can be full of blue light where the bounding light is white. The difference between filling up and filling becomes clear when contemplating the filling of a shadow with the same colour and intensity of that of the hole-lining. The shadow disappears. Another example is a round hole of a metre in diameter cut into a brick wall. In order to fill in the hole in the wall, we might consider that it must be filled with a sufficiently similar arrangement of bricks and mortar to that which constitutes the existing wall. Yet another example is a sphere with a cavity at its surface. To fill in this hole would seem to require similar material to that which constitutes the sphere, sufficient in volume and shaped to remove any discontinuity from the surface of the sphere.
It should be apparent from these few examples above that normativity has been snuck into the distinction between filling in and merely filling up. It seems that the distinction rests on ways that a host ought to be in some idealisation. Light and brick walls ought to be uniform and continuous. Spheres ought to be completely round. This normativity is not to be confused with the telos or proper function of a thing because the proper function of a thing might require that a thing have holes in it. An obvious example is the proper function (if there is such a proper function) of organs such as the heart or ear. A heart may have the proper function of pumping blood and, yet, there is a sense in which the heart’s irregular shape and the presence of holes makes it a less than perfect solid. The idealisation of certain uniform shapes and constitutions therefore goes beyond – though it may include – the idealisation of function. Indeed, idealisations may pull in different directions, just as an ideal solid would make a less than ideal heart. Having clarified that the relevant normativity is idealisation, broadly construed, the question becomes one as to whether or not holes may be fully explained by idealisations of certain material forms.
The idealisation of certain material forms is not sufficient to explain the distinction between filling in and filling up a hole because the addition of missing parts is not all there is to attaining an ideal form. For example, an otherwise perfect sphere could have a protrusion in exactly the same shape as the cavity in the previous example of a sphere, save for its inversion at the surface of the sphere – a horn, say. So, idealisation need not involve the filling of a hole, or the filling of any vacancy, for that matter. It may simply require the filing down of a protrusion, i.e. it may require an absence to be instated. Thus, holes cannot be reduced to a relation between actual and ideal things as such a relation is not sufficient to distinguish between holes (deficits) and protrusions (overabundances). Our ability to identify a relation between a host, a hole and an idealisation of the kind or kinds of thing the host is does not explain the hole but presumes that absences such as holes are in or about the host. Such a ternary relation privileges one amongst among an infinite number of absences, the infinite array of things that are also absent from the spatial region of the hole, to make one absence the absence that is the hole. In the case of holes and other absences, the choice between realistic and conventional accounts of the normativity of idealisation is a choice between the privileging of one absence among many by means of some objective relation between the things in which there is a hole and the relevant absence, or by means of the inter-subjective practices of a community. It is not the same choice as that between treating holes and absences as real things or as merely conventional posits. It might be thought that the example of organs such as a heart is sufficient to challenge the objectivity of idealisations. The ideal form of a heart can pull in opposite directions in being more like a pump or more like an ideal solid. Not only such conflicting idealisations but, vagueness as to what is and what is not ideal for a given thing, seem to favour conventionalism as to idea forms. However, these are not reasons for a stance on whether or not absences should be regarded realistically, but whether or not absences (which may in any case be regarded realistically) should be privileged in the idealisation of a hole-host by objective or conventional relations.
If idealisation as it relates to determining the material required to fill in a hole is but the privileging of one amongst an infinite number of relevant absences then the next question arising is what the usual relation is supposed to be between those infinite number of absences, whether privileged or not, and the hole-host. Miller(15) also motivates her conventionalism about holes by means of an equivalence of warrant for opposing views as to whether holes are negative parts of their hosts, as proposed by Hoffman and Richards(16), or parts of a larger immaterial thing made of the space-time region that surrounds and partly coincides with the hole-host, as proposed by Casati and Varzi.(17) However, there is a third view of the relation between holes (privileged or otherwise) and hole-hosts that Miller does not consider. In the discussion above of the view of Martin and Kukso that absences are spatially located, it was suggested that this was to confuse properties of an absence with properties of that of which it is an absence. It is suggested that both the view of Hoffman and Richards and that of Casati and Varzi are founded on a similar error. A hole is not a part of its host, or a part of something made of a larger region of space-time; a hole is the absence of something as part of the hole-host. That is, a hole is the absence of the state of affairs of some specific thing being part of the hole-host. The “ontological” dependence of holes on their hosts turns out to be nothing beyond the same ‘of’ relation that holds between any absence and that of which it is an absence.
Notes
1. Martin, C. B., ‘How it is: Entities, Absences and Voids’ (1996) 74/1 Australasian Journal of Philosophy pp. 57-65
2. Ibid. p. 58
3. Kukso, B., ‘The Reality of Absences’ (2006) 84/1 Australasian Journal of Philosophy pp. 21-37 at pp. 22, 29
4. Martin, C. B., ‘How it is’ p. 64
5. Kukso, B., ‘The Reality of Absences’ pp. 29-30
6. Lewis, D. & S., ‘Holes’ (1970) 48/2 Australasian Journal of Philosophy pp. 206-12
7. Fowler, G., Spencer, J. & Wake, A., ‘Holes as Regions of Spacetime’ (2007) 90/3 The Monist pp. 372-8 — Miller, K., ‘Immaterial beings’ (2007) 90/3 The Monist pp. 349-371 at p. 355
8. Casati, R. and Varzi, A. C., ‘Holes and Other Superficialities’ (1994) MIT Press: Cambridge, Mass; London pp. 13, 18-9
9. Ibid. pp. 32-6
10. Sorensen, R., ‘Seeing Dark Things’ (2008) Oxford University Press: Oxford; New York etc. p. 190
11. Casati, R. and Varzi, A. C., ‘Holes’ pp. 56-7
12. Miller, K., ‘Immaterial beings’ p. 358
13. Ibid. p. 365-7
14. Sorensen, R., ‘Seeing Dark Things’ pp. 188-90
15. Miller, K., ‘Immaterial beings’ pp. 364-5
16. Hoffman, D. D., and Richards, W. A., ‘Parts of Recognition’ (1984) 18 Cognition pp. 65-96 at 85
17. Casati, R. and Varzi, A. C., ‘Holes’ pp. 56-7