Presentism draws you in. When you first become acquainted with the presentist view of time it’s hard not to concur that this is how time must be. What is it that makes the presentist theory of time so compelling? Its appeal is often said to reside in the way that it illuminates the temporal aspect of human experience. Psychologically, there is something special about the present. All of our thoughts, feelings and actions occur there. Past joys and hurts become less palpable and visit us more and more infrequently as they recede into distant memory, while past visions and sounds ebb into dullness and pallor. The future is more elusive and even less tangible than the distant past. We often try to sniff it out, striving to locate it, yet not for what it is, only for what it will be. But present awareness is fresh, immediate, lustrous, and sometimes, exciting in a way that past awareness never is. Given the psychological uniqueness of the present it is therefore tempting to imbue this specialness with ontological import—to make this psychological centrepoint a centrepoint of our metaphysics. The presentist does this, but not merely by elevating the metaphysical status of present states of affairs above all other temporal states of affairs. Rather, other temporal states of affairs are ontologically excluded.
The primary aim of this paper is to present a new difficulty for presentism. I will argue that, contrary to appearances, a central feature of our psychology, namely conscious experience, embodies a significant obstacle to presentism. I claim that this obstacle can be overcome only if the presentist is willing to embrace some form of mind/body dualism. And insofar as mind/body dualism is unattractive, so too is presentism.
Here are the two basic tenets of presentism:
(1) Nothing that is past or future exists.
Accordingly, though we exist, neither our deceased forebears nor our unconceived children exist.
(2) There is change with respect to which facts characterise the world.
To illustrate this, consider my neighbour’s dog, Conan. It once was a characteristic of the world that Conan barked incessantly. It is at this very moment a characteristic of the world that he is on an operating table somewhere having his vocal cords severed. And it soon will be a characteristic of the world that Conan is a non-barking animal (though he will still probably move his jaws a lot). (2) is what makes presentism a tensed theory of time: any metaphysically accurate survey of the world must be formulated using the tenses, since it is these that convey how the world is, as distinct from how it has been in the past and how it will be in the future.
(1) and (2) set presentism apart from its main rival, the tenseless theory. If the world has a history or a future then according to the tenseless theory there are past and future entities as well as present ones. Furthermore, there is one set of facts that eternally characterises the world. Once we have described in full detail the various entities in the world and set out the relations (including temporal ones) that obtain between them, we have said all that there is to say about the world ‘once and for all’. That is the end of the story; no other set of facts did, nor will, characterise the world. The denial of (2) makes the expression, ‘the tenseless theory’ apt, since, according to the tenseless theorist, a metaphysically accurate survey of the world is to be given without recourse to tenses.
Where does the attraction of presentism lie? The psychological privilegedness of the present has already been noted. There are routes to presentism from this psychological privilege. A simple route is to claim that presentness is a phenomenal property; we can directly apprehend that our experiences have the monadic property of presentness. However, the view that there is a property of presentness is not shared by most presentists.
A related, but less crude, path to presentism flows from more theoretical considerations. There appears to be a powerful case for presentism if it can be shown that certain aspects of our psychology could not be properly explained if presentism were false. Over the course of our lives we have a great number of experiences. Yet, if the tenseless theory of time is correct, all of these experiences are ontologically on a par. If none of our experiences are ontologically privileged, then why are they not psychologically on a par? Why do we discriminate phenomenally against past and future experiences? [Ferré 1972: 435–6.] And if there is no change of the facts that characterise the world, then how do we explain the unease which rises up in us as we anticipate an unpleasant event that is inexorably approaching us, and the wonderful sense of relief that accompanies its ending? [Prior 1959]
It might be argued that these considerations do not lead directly to presentism. There are other tensed theories of time which ontologically privilege the present, but not by ontologically excluding the past, or in some cases, even the future. Such theories treat presentness as a special transient intrinsic property. Elsewhere, I have argued that despite appearances such theories don’t mark any advance over the tenseless theory when it comes to addressing these considerations [McKinnon 1999].
Other reasons have been given for embracing presentism which are not so closely tied to psychological matters. Sometimes, for example, it is thought that only presentism affords us with an adequate response to McTaggart’s Paradox [Christensen: 1974].
I will not mention any further motivations for presentism, as it is not my purpose here to be exhaustive in this regard. I have emphasised in particular those motivations arising in connection with our phenomenal experience, because, as I will explain later, issues surrounding the metaphysical basis of consciousness actually turn out to yield considerable negative consequences for the presentist.
Having briefly introduced presentism and some motivations for that view, I turn next to some further relevant details concerning the metaphysics of presentism.
It is often noted that the words ‘now’ and ‘present’ have no fixed usage in everyday discourse. Sometimes, it seems that they are meant to indicate a very brief span, as in the following example:
Jamie stares listlessly from his rumbling carriage. The monotony of the lifeless desert sands remains, as it has for the last several hours, unrelieved. Wrenching his gaze from the window, he attends to his shoes. Just now, an amusement park hurtles by.
In other situations they might be used to encompass longer periods. Consider a commander speaking to his troops on the eve of a pivotal battle: ‘Now is our last chance to repel the enemy’, he says as he exhorts them to one last effort. Evidently, he does not intend his use of ‘now’ to be as temporally restricted as its use in the previous example. In this context, ‘now’ suggests a period extending from the time of utterance until the result of the battle is beyond doubt.
Granting the apparent context-dependent nature of ‘present’ and ‘now’ as they feature in ordinary discourse, we might be curious about how the presentist uses these words. When the presentist says that the only temporal items in existence are present ones, what does this amount to?
While doing metaphysics, the presentist’s sense of ‘present’ is not one whose temporal extent varies according to context. If it were, then what exists could vary from context to context. I take it that the presentist prefers not to conclude that we can talk things in and out of existence merely by shifting contexts. So, the presentist must have in mind a special, fixed sense of the present—the metaphysical present, if you like. What, then, is the scope of the metaphysical present? Surely it is not so broad as to include the Age of the Dinosaurs, the Big Bang and the extinction of our sun. This would be to make presentism too much akin to the tenseless theory of time. Just how narrow must it be?
It is often thought that the presentist should conclude that the metaphysical present has no scope; that figuratively speaking, it is a knife-edge separating what has been from what is yet to come. In other words, the metaphysical present is temporally unextended. The justification for this view traces back to Saint Augustine [Augustine 1991: 232]. Here is what I take to be the essence of Augustine’s influential argument. If the present is extended then it has wholly distinct parts and those parts must be simultaneous. This rests on the assumption that if x and y are both metaphysically present then they are simultaneous. On the other hand, if the present is extended then it also seems that its disjoint parts cannot be simultaneous: if x and y are not temporally overlapping then they are temporally separated and hence, not simultaneous. Thus, we have a reductio of the view that the metaphysical present is extended.
If Augustine is to be believed, the presentist must regard the present as temporally unextended. I have some reservations about whether Augustine’s argument licenses this conclusion (see §10), but I will put these aside for now; as far as I know, no presentist has suggested in print that the present is durational. As we will soon see, the metaphysical nature of consciousness leads to problems for the view that the metaphysical present is unextended. It turns out that there are reasons for thinking that conscious experience is always temporally extended.
On the hypothesis that the metaphysical present is durationless it follows that any conscious experience we are having must itself have no metaphysical duration. But do we really have durationless conscious states? At this point, it is important to eliminate a possible source of confusion about this question. I will now outline an unsatisfactory, but instructive, argument against presentism. Isolating the flaw in this argument will help us to remain clear about what is at stake.
Echoing Kant, William James observes that there is a significant difference between a mere succession of awarenesses and an awareness of succession [James 1981: 591]. To illustrate this point, suppose that we have a series of awarenesses. Further suppose that each of these awarenesses is a phenomenal island, untinged by vestiges of past awareness. In that case, we would not have any conception of one thing following another, and hence, we would have no conception of change. So what is required for us to have a conception of succession, and therefore, of change? Here, James quotes Volkmann with approval:
…if A and B are to be represented as occurring in succession they must be simultaneously represented; if we are to think of them as one after the other, we must think them both at once [James 1981: 592].
Thus, for two states of affairs to be represented to us as occurring successively, the first must leave a trace behind, so that when we become aware of the second, this awareness of the second is juxtaposed with an awareness of the first. Thus, James thinks that the span of our phenomenal present is far from being a vanishing point. In his opinion, the breadth of this present can be anywhere from a few seconds to a minute [James 1981: 603].
Suppose that James is right. The mistaken argument against presentism concludes that since our phenomenal present has temporal breadth, so too does the metaphysical present. The problem with this argument is that it conflates the distinction between content and its bearer. A written token of ‘loud’ represents loudness, but the bearer of this content is not itself loud. In the case that interests us, even if we think that the content of our phenomenal present represents past and present things as co-existing, it remains an open question whether our phenomenal present qua bearer of this content has metaphysical extension. The presentist can claim that the bearer is metaphysically durationless. To make things uncomfortable for presentists, it must be argued that the bearers of conscious states have temporal extension. It is to this task that I now turn.
In this section, I will discuss prima facie reasons for thinking that the neural correlates of consciousness, namely, those neural phenomena which are direct correlates of consciousness, are temporally extended. Later, I will discuss what implications this might have for consciousness itself. To help locate the ensuing discussion, a very brief overview of the cerebral cortex is worthwhile, since this is where the neural correlates of consciousness are most likely to be found.
Two separate sheets of nerve cells, one on each side of the brain’s exterior, make up the cerebral cortex. The surface area of these sheets is sufficiently large that they must be folded to fit inside the skull. This folding accounts for the brain’s characteristic walnut-like appearance. Functionally speaking, the cortex is strikingly modular. There are separate regions devoted to processing information from each of the sensory modalities, namely, sight, touch, smell, taste and hearing. Moreover, at least some of these regions are also modular. For instance, specific visual functions have been assigned to more than twenty cortical areas. There are separate regions devoted to handling colour, shape, contrast, orientation and movement. As Singer puts it:
Depending on the features constituting the object (of perception), neurons become activated in different, often noncontiguous cortical areas, and it can be predicted that even simple visual patterns will give rise to simultaneous responses in a vast number of (widely distributed) neurons [Singer 1994: 80].
The brain itself is composed of billions of interconnected nerve cells, or neurons, and information is carried and disseminated throughout the brain by these cells. Each neuron has a protruding fibre called an axon, whose firing transmits information to adjoining neurons. It also has other fibres called dendrites, which receive information from the firing of adjoining neurons. The neural correlates of consciousness are those neuronal activities that are directly correlated with consciousness. Of special interest to us is the way in which neurons encode information. It turns out that much of this coding is temporal as well as spatial, as I will now explain.
It has been known since the 1920s that at peripheral levels of sensory systems single neurons represent fixed stimuli; the firing of a given peripheral neuron always codes for the same sort of sensory stimulus [Adrian and Zotterman 1926]. The intensity of that stimulus is registered by the average firing rate of that neuron over a brief period of time; the stronger the stimulus, the higher the firing rate. It is not, however, plausible to think that all, or indeed, many, representations at higher levels of processing, such as those which correlate with conscious states, are signalled exclusively by one neuron. A single-cell code precludes generalisation from old representations to new ones. This is a severe problem, since the system will hardly ever be presented with exactly the same stimulation on multiple occasions [Fotheringhame and Young, 1997: 49]. There is also a combinatorial problem. Even if we restrict ourselves to visual stimulation, it is unlikely that there would be enough neurons in the brain ‘if all distinguishable objects, including their many different views, each had to be represented by a specialized neuron...’ (Singer, 1994, pp. 80–1). Thus, it is likely that higher-level representations embody assemblies of co-active neurons.
Although it is unlikely that the brain employs single-neuron codes on a large scale, important roles have commonly been assigned to coding by firing rate (rate coding) at all levels of processing. It has, for instance, been widely held that colour and form are represented by rate codes [Burkhalter and van Essen 1986]; [Hubel and Livingstone 1987], and that the perception of motion is rate encoded [Koch and Crick 1994: 98].
Moreover, evidence has been growing to suggest that coding in the temporal domain is not restricted to codes of average firing rate. Two neurons sharing the same average firing rate over a certain period of time might have firing patterns that differ markedly when considered in fine detail. In a rate code these differences are regarded as noise, contributing nothing to the information content of the code. However, it is plain that in principle, at least, these differences in the temporal relationships between individual firings could constitute differences in information content. Let us call this potential means of coding timing coding. Evidence for the timing coding of contrast (e.g. the contrast between figure and background) has been presented in [Richmond 1997] and [Mechter et al. 1998].
It appears that there are good reasons for thinking that the neural correlates of many conscious states are temporally extended. So we can conclude that many conscious states are themselves temporally extended. Yet, the presentist says that the metaphysical present lacks temporal extension. Therefore, we can conclude that presentism lacks the ontological resources to adequately support consciousness. And since it is clear that there are conscious states, it can be concluded that presentism is falsified.
This is a pleasingly simple argument, but it is much too eager to reach its conclusion. One response might be to observe that the neural correlates of consciousness are just that, namely, correlates of consciousness. We need a bridging argument to justify the conclusion that conscious states themselves have temporal extension. An example would be an argument for some form of mind/body identity theory. However, this would not be a dialectically useful response, since it concedes that something has temporal extension, namely, the neural correlates of consciousness; that concession alone is enough to cause problems for presentism.
A better response is to note that presentists admit certain analogues of temporal extension which might be capable of standing proxy for the concrete temporal extension favoured by tenseless theorists. The thought is that these resources might allow the presentist to do justice to the temporal features of the neural correlates of consciousness without conceding that anything has temporal extension. Thus, much still needs to be done to show that presentism is in trouble. I will first argue that if an identity theory of mind/body is correct, then presentism does not in fact have the resources to plausibly account for consciousness. I will then consider what prospects there are for presentism in the absence of an identity theory.
First, I will make a few amplifying remarks about identity theories of mind. Those who favour physicalism generally prefer some sort of identity theory. Old-style physicalists preferred a type identity theory, where a certain type of mental state is identified with a type of physical state. This seemed a little severe since it meant that organisms with physiologies different from humans could not share the same sorts of mental states. The intuition that a certain mental state could be realised in different ways led to functionalism. According to functionalists, a mental state is defined in terms of its functional relationships with the outside world and with other mental states. Sometimes, this leads to a token identity theory, where particular tokens of mental states are to be identified with particular tokens of physical states, but no type identities obtain. Sometimes it leads to the identification of particular mental states not with their physical realisers, but with functional role states. On this view, mental states are not identical with the physical states that realise them, but are nevertheless constituted by physical states. What I say about the temporal properties of conscious states according to the identity theory carries over to this view, since the spatio-temporal properties of mental states on this view are coextensive with the spatio-temporal properties of their realisers.
Now, consider the following example. Suppose that you are reclining outside on a beautiful summer’s day with the Sunday paper beside you. You gaze sleepily out at the clear blue sky. The neural correlates of your colour-experience involve either rate or timing codes. Either way, the neural correlates of this experience seem to be temporally extended. On the assumption of an identity theory, the conscious state is itself temporally extended. The tenseless theory of time accommodates this fact quite easily. Your experience is spread out in time; its earliest part is no less existent than its latest part. Presentists have to say something different, since they say that the metaphysical present is unextended. We will now see how presentists might try to do without temporal extension.
Since presentists hold that nothing past or future exists, they generally construe facts ostensibly about past and future entities as disguised facts about existing things. Some facts about putative past or future states of affairs, for instance, can be expressed purely in terms of entities that were or will be constituents of those states of affairs. John Major’s having been Prime Minister of the United Kingdom, for instance, can be expressed in terms of a certain relationship between John Major and the property of being Prime Minister of the United Kingdom. John Major has the property of having instantiated the property of being Prime Minister of the United Kingdom. Other ostensibly past and future states of affairs are not so easily accommodated. Consider the past-tensed state of affairs of the horse Phar Lap’s having been a Melbourne Cup champion. Phar Lap no longer exists according to the presentist, so something else that does exist has to be found to act as a place-holder for him. There are a few things we could try here. We could say that the fact that Phar Lap was Melbourne Cup Champion is really a fact about his stuffed hide, now residing in the Melbourne Museum, which was once the skin of a horse that won the Melbourne Cup. Or we could say that it is really a fact about Phar Lap’s haecceity, which was once instantiated by a horse that won the Melbourne Cup. We could even say that it is a fact about the world as a whole that it once contained a horse which won the Melbourne Cup.
How could this sort of presentist handle the case of your blue sky experience? To simplify things, let’s pretend that your blue sky experience consists in the firing rate of a single neuron over a certain period of time. Since in this case the neuron which supports this experience still exists, there is no need to invoke recondite entities like haecceities or world-properties. The neuron itself has various past (and perhaps even future) tensed properties like having fired a certain time ago, a certain time ago before that, and so on. On this view, the conscious state consists in the instantiation by the neuron of a conglomerate of past, and perhaps future, tensed properties, along with how it is in the present. So the conscious experience is largely composed of non present-tensed states of affairs about how the neuron was or will be. On the face of it, this is very peculiar. We are asked to believe that a present conscious state could be composed mostly by facts about what no longer obtains, or what does not yet obtain.
Even worse, it seems to allow that a conscious experience could be made up entirely of past or future-tensed facts. After a neuron fires, there is always an interval during which it is not firing. Consider some moment, in the middle of a sequence of firings that constitute your blue sky experience, when the neuron is not firing. Do we say that you are having your experience at that moment? If we say yes, then that experience is composed entirely of non present-tensed states of affairs about the firing of the neuron. Can we say no? It’s hard to see how. If we say no, then we are saying that you can have the blue sky experience only while the neuron is firing. But this seems unjustified. A single firing of a neuron makes no significant difference to the average firing rate of the neuron, and it is this average firing rate which constitutes my experience. So it is hard to see why the matter of whether the neuron is currently firing or not should make any difference to whether or not you are having the experience. Thus, it seems that the presentist has no good reason for denying that conscious experience could involve only non present-tensed facts.
Note also that the problem of conscious states being composed by past (or future) tensed states of affairs is not merely one of peculiarity. Past tensed states of affairs cannot be constituents of present tensed states of affairs like your blue sky experience because they lack the right structure. The present tensed state of affairs that the neuron is in a firing state registers a fact about how the neuron is. However, a past tensed state of affairs to the effect that the neuron was in a firing state two seconds ago is a fact purely about what happened two seconds ago. It conveys only that two seconds ago the property of being in a firing state was instantiated by the neuron. And this is not the right kind of structure to be a constituent of fully-fledged present tensed states of affairs like your blue sky experience. Here, it is useful to compare past-tensed states of affairs to modal states of affairs. For the same sorts of reasons we would not like to think that a fully-fledged existing entity could be composed mostly by states of affairs about what is merely possible. So, for instance, we would not be happy to think of my blue sky experience as being composed mostly by states of affairs about what is merely possible for the neuron.
It is worth mentioning that not all presentists think that past or future tensed facts need to be facts about something that now exists. In the tradition of Meinong, some presentists have held that non-existent entities possess properties and stand in relations, either with existent entities or with other non-existents. According to this view, the fact that Phar Lap won the Melbourne Cup is a fact about Phar Lap, even though Phar Lap no longer exists. Exactly what sort of properties can non-existents have on this view? Usually it is held that most ordinary properties, such as having hair and being made of wood, are indeed existence-entailing. Properties that are not thought to be existence entailing are properties like being the subject of propositional attitude ascriptions and the properties of having ordinary properties in the past and future [Salmon 1998: 290–1]; [Hinchliff 1996: note 17].
There are a couple of ways in which this sort of presentist might construe your blue sky experience. One way might be to identify it with how the neuron is presently, along with various non-existent states of affairs dealing with how the neuron was in the past, and perhaps, how it will be in the future. However, it is more than hard to believe that a conscious state qua aggregate of states of affairs could exist unless all of its parts exist; an existing aggregate must have existing parts. A better idea would be to identify the experience with present and non present-tensed facts about the neuron itself. One such fact might be the past-tensed fact that the neuron was a constituent of a certain now non-existent firing of that neuron. Notice that this idea closely resembles the account of your blue sky experience attributed to presentists who believe that all properties are existence-entailing. The only difference is that here the relevant non present-tensed facts are facts about the neuron and non-existent states of affairs, rather than facts about the neuron and the property of neuronal firing. So the problems I raised earlier for thinking of conscious states as being made up of non present-tensed properties apply here also.
At this point, it might occur to presentists that I have misconstrued their position, and that this misconstrual is responsible for the difficulties just outlined. To explain this thought we need to discuss the presentist treatment of events.
Imagine you are a servant at the court of Henry VIII. At the end of a rather large meal he gorges on a dismembered chicken. He raises a hand from his fulsome belly and passes it lethargically across his mouth, signalling the end of his transaction with the plate. After rubbing his greasy fingers indelicately through his beard he settles back. And then he lets out the loudest, longest belch you have ever heard. Just as it is reaching its apex, you whisper to yourself, ‘That’s some belch!’
For tenseless theorists, the belch taken as a whole is part of the furniture of the world. This event has earlier and later parts, ranging from the first tones that puncture the silence and the crescendo that rapidly builds, through to the stunningly sustained apex and the gradual release into a low, self-satisfied rumble. Each of these parts exists, and thus, the temporally extended sum of these parts exists. In other words, the belch exists. Presentists cannot say this, since it is never the case that more than one configuration of Henry’s lungs, vocal cords and mouth exists. Presentists regard talk that seems to imply the existence of events as elliptical talk about existing things and what is happening to them [Prior, 1968]. So, when you whisper mid-belch, ‘That’s some belch!’, you are not implying that a belch qua event exists. You imply only that Henry is in the process of belching. But it is never the case that there exists something that is a belch.
Taking these facts into consideration, it might be claimed that I have simply misrepresented presentism. I began by arguing that if an identity theory of the mind is accepted, then prima facie your blue sky experience has temporal extension. It could be said that I went some of the way towards accommodating presentism when I wondered whether that experience could be wholly located in the metaphysical present, albeit at the cost of including non present-tensed states of affairs as its constituents. But perhaps I did not go far enough. In my dim way I continued to treat experience as if it were some kind of entity. Had I followed things through properly, it would have become clear that if experience is something that happens over time, then for the presentist there is no existing series of neuronal firings that responds to blue; there is only one neuronal state existing after another. So, just as there is the property of being in the process of belching, there is the property of being in the process of experiencing blue. And just as there are no belches, there are no blue sky experiences. Therefore, the arguments presented earlier against the thought that your blue sky experience could be situated in the durationless metaphysical present were misdirected.
In general, I have no quarrel with the presentist’s distaste for reifying changes and processes. In terms of serving our everyday practical interests, it usually makes no difference whether we think of changes and processes as entities (things which exist). When we say that a thing has changed in some way, our interest is just in contrasting the way the thing is before the change with the way it is after the change. When we talk of a thing’s having undergone a certain process, the nature of our interest is a little broader. We do not care simply about the contrast between how the thing is before and after it has undergone the process. We care also about how it went from being in its pre-change state to its post-change state. And this involves our being interested in the sequence of states that the thing is in while it is undergoing the process. None of these considerations, however, suggest that in terms of our practical involvement with changes and processes it matters to us whether changes exist. I may care, for instance, that the traffic light has changed from green to red, but for all practical purposes, it does not matter whether there is an ordered pair of light states, ágreen, redñ, which exists and can be identified with the change.
I doubt that avoiding the reification of changes produces deep metaphysical difficulties for presentism. However, I claim that the processes directly involved in the production of consciousness are special cases. Under the assumption of physicalism, the failure to reify these processes commits us to the elimination of conscious experience.
Just as tables and chairs exist, so do qualia. If physicalism is right, then qualia are in fact sequences of neuronal firings. And if qualia exist, then these sequences of neuronal firings must also exist. But if presentism is right, then we cannot reify such sequences.
Do qualia really exist? Suppose you are playing cricket. You are fielding in an attacking catching position. As such, you are very close to the batsman. In fact, if the bowler bowls a poor delivery and the batsman aims a hefty swing in your direction (and bat meets ball) you are almost defenceless. And this is just what happens. The ball hits you on the thigh and sharp pain coruscates through your leg. I claim that the pain you feel exists. I claim that you have non-inferential warrant that it exists. Moreover, it is not obvious that there is good reason for accepting cricket bats, balls and bruised legs in your ontology but excluding pains. Certainly, I think that the burden of proof lies with those who wish to give bats and pains a different ontological status.
Of course, the fact that I make these claims does not guarantee their truth. I suspect that some people will agree with me on these points, but that, perhaps, others may demur. It is hard to argue for claims of non-inferential warrant. And notoriously, there is often disagreement over such claims. In order to reach a dialectically satisfying position I need arguments. To that end, consider the following cases.
Case 1. Alan is dawdling along the street when he is hit by a distracted cyclist. It hurts. Alan continues to feel pain for some days.
Case 2. Alan is hit by the distracted cyclist. From t1 to t2 he undergoes the minimal amount of neural activity required for him to feel any pain whatsoever. Immediately after, he is obliterated by an errant cruise missile.
Case 3. Like Case 2, except that at some t between t1 and t2, (before he has completed the minimal amount of neural activity required for him to feel any pain whatsoever) Alan is obliterated by an errant cruise missile.
Look at Case 2. The presentist needs to say that no pain exists, but that between t1 and t2 Alan is in the process of experiencing pain. Now transfer your attention to Case 3. Take an arbitrarily selected t between t1 and t2. What does the presentist say about whether, at t, Alan is in the process of experiencing pain?
There appear to be two options; Alan is not in the process of experiencing pain or he is in the process of experiencing pain. Consider the first option. If we say that at t in Case 3 Alan is not in the process of experiencing pain, then how do we justify saying that at the corresponding time in Case 2 Alan is in the process of experiencing pain? The only way, it seems to me, of supporting an asymmetry between the cases is by appealing to those future-tensed facts about Alan’s neural activity which obtain in Case 2 (but not in Case 3). And this is dubious because it looks as though, at t in Case 2, Alan has the property of being in the process of experiencing pain in virtue of things that will happen to him. And this is suggestive of backwards causation. And invoking backwards causation for normal cases of conscious experience is most undesirable. Even if this objection is wrongheaded, I still suspect it is implausible to say that Alan is not in the process of experiencing pain at t in Case 3. I will now motivate this suspicion.
Consider the second option, according to which Alan is, at t in Case 3, in the process of experiencing pain. I think that this is the correct option to take. However, I will argue that this in fact turns out to be a consideration against the presentist metaphysics of conscious experience. Compare Case 3 with an adjunct to Case 1:
Case 4. Jonas is changing a wheel on his bicycle which was damaged by a collision with a dawdling pedestrian. Just as he removes the warped wheel he is obliterated by an errant cruise missile.
Jonas did not finish changing the wheel. Does that mean that he was not in the process of changing the wheel when the missile arrived? It does not. It is not usually a condition of being in the process of R-ing that the process ends up being completed. What sort of conditions are there, then? I will mention two. First, and most obvious, is that completion of the process is possible. If I start following a diet and exercise regime with the intention of weighing eighty and eighty-five kilograms simultaneously, then when I give up after a couple of months, no one is going to say that I was, before I gave up, in the process of becoming eighty and eighty-five kilograms. Second, I suspect, is some sort of counterfactual completion condition. I am not going to try and specify that condition in detail here. However, in very broad outline, we would say that Jonas was in the process of changing a wheel because Jonas was a competent wheel changer, and if things had gone along as they usually do when competent people try to change wheels, then Jonas would have completed the process.
Thus, I also think it is reasonable to agree that in Case 3, Alan was in the process of experiencing pain at t; had a wildly improbable event not intervened the process would have been completed. Tenseless theorists can use similar reasoning and agree that at t Alan was in the process of experiencing pain. For the tenseless theorist, there is an existing sequence of neural states, s, which, while not actually comprising an experience, could have been parts of an experience. And had Alan not been obliterated at t2, s would have been part of an experience.
Tenseless theorists can therefore distinguish between being in the process of experiencing pain and having a pain experience. And this is important, because, if the neural picture I have presented is correct, then a person can be in the process of producing conscious experience without thereby succeeding in producing it; Case 2 is an example of success, whereas Case 3 exemplifies failure.
Presentists are not in a position to draw this distinction. The only way that presentists have of parsing phenomenal vocabulary is in terms of being in the process of having an experience. And as I have already indicated, this does not give us the resources we need to classify Case 2 as one where there is phenomenal experience and Case 3 as one where there is not.
I have argued that presentism is not compatible with mind/body identity theories. An important part of my argument involved the view that presentism is committed to the present’s having no temporal extension. The motivation cited for this view was Augustine’s argument. Perhaps it is time to re-evaluate that motivation. I doubt that it is ironclad. I will argue that a presentist can coherently hold that the metaphysical present has duration. However, I will also argue that ultimately, coming to this realisation does not help to square presentism with physicalism.
It is assumed in the premises of the argument that any stretch of time may be divided into further stretches of time. Perhaps this assumption could be questioned. Certain ancient Greeks questioned it. They maintained that there are atomic intervals—that is, intervals which have no proper parts. If presentists adopt this view, they can say that the present is indivisible even though it is extended. And this means that the presentist is not touched by the attempted reductio, since it depends upon the falsity of temporal atomism. But we can see that this is not going to help the presentist. For what matters here is not merely that the present has extension, but that it has parts. The neural correlates of consciousness have distinct temporal phases. A durational present without parts does not have the mereological structure required to support the neural correlates of consciousness. Temporal atomism is not helpful.
However, I doubt that we need to resort to temporal atomism in order to find a version of durational presentism that is coherent. The view that the metaphysical present has duration and has parts is coherently describable. Once this view has been properly described, it turns out that Augustine’s objection rests on an equivocation. Before this point can be established, however, it is necessary to flesh out the notion of durational presentism.
Consider an interval which has as parts every interval that exists. This interval indicates the boundaries of the present. Let’s introduce a special technical expression to denote this sort of interval: let’s call it a big interval. As time passes, there is change with respect to which set of intervals exists, and therefore big intervals pass in and out of existence. To distinguish the picture we are developing from the atomistic view previously considered, we will stipulate that big intervals are not atomic—they have proper parts.
Note that I am assuming a reductionist view of the nature of instants and intervals. I mention this because what I have said above may sound confusing if the reader has in mind a substantival view. Here, instants and intervals are being construed as constructions from their ‘contents’. Thus, any change in terms of what exists, marks the destruction of one big interval and the generation of another. This way of putting things is purely a matter of convenience. A substantival view of instants, according to which instants and intervals are entities distinct from their contents, could just as easily have been assumed. On a substantival view, there would be no reason to talk of big intervals going in and out of existence. We would merely speak of their contents as changing.
Now, suppose that we are interested in the details of how big intervals pass in and out of existence. We might start by dividing the ways in which big intervals pass in and out of existence into two broad versions. Each way, I will argue, can be defended from Augustine’s objection.
According to the first version, when a big interval goes out of existence it leaves nothing behind. More precisely, no part of a big interval will be a part of the next big interval. According to the second version, a big interval does leave something behind. It goes out of existence by losing a proper part, thereby making way for a new big interval. Putting this second view more pictorially, think of the present as a worm that gains segments at one end while losing them at the other. A segment is ‘born’ at one end of the worm and passes along the length of the worm to the other end, where it is annihilated. To each such generation and annihilation corresponds a distinct big interval.
Now, recall the two principles that were crucial in the reconstruction of Augustine’s argument against a durational present:
(1) If x and y are present then they are simultaneous.
(2) If x and y do not temporally overlap then they are not simultaneous.
I think that a defender of durational presentism ought to say that (1) and (2) equivocate over ‘simultaneous’.
According to durational presentism, time has two importantly different aspects. First, there is the concrete temporal extension embodied by the big interval. The big interval is made up of sub-intervals and instants, such that these sub-intervals and instants (and their contents) stand in relations of precedence and simultaneity to each other. Second, there are tensed facts about how the contents of the big interval were, how they are, and how they will be.
The durational presentist ought to connect the sense of ‘simultaneous’ in (1) with the second aspect. Thus, the correct understanding of ‘simultaneous’ in (1) is as follows:
x is simultaneous1 with y iff x and y are present.
On the other hand, the sense of ‘simultaneous’ relevant to (2) ties in with the first aspect:
x is simultaneous2 with y iff x and y are located at the same concrete moments of the big interval.
Once we distinguish these two senses of ‘simultaneous’ we can agree x and y’s being present and non-overlapping entails that they are simultaneous1 and non- simultaneous2. But since it is consistent for x and y to be simultaneous1 and not simultaneous2, no contradiction can be derived in Augustine’s way from durational presentism.
Given that durational presentism survives Augustine’s argument, how does it fare with respect to squaring presentism with physicalism? First, consider the version which says that when a big interval goes out of existence, it leaves nothing behind. An apparent drawback to this view involves the question of what makes one end of the big interval the earlier end, and the other the later end. Since each big interval comes into existence complete, as it were, it seems that an account has to be given which is separate from the story about the passing of big intervals in and out of existence. This is likely to be unattractive to many presentists qua tensed theorists, who prefer to account for any talk of earlier/later in terms of tensed notions.
There is another drawback to this view, which pertains to consciousness. Suppose that Kate is such that whenever she has an experience it is always neatly enclosed by the metaphysical present. Let l stand for the length of the metaphysical present. Now suppose that Kate’s entire life were shifted backwards by l/2. In an intuitive sense, Kate would have had the same neural history, but she might have no conscious experiences whatsoever, because the contents of the metaphysical present never have the right properties.
Notice that these reservations need not apply to the other version of durational presentism. This version says that big intervals go out of existence by losing proper parts. The question of why one end of the big interval is the earlier end and the other is the later end can be answered without having to appeal to anything outside the passing of big intervals in and out of existence. We can simply say that x is earlier than y iff x and y exist and x did exist while y did not exist. One unusual consequence of this view is that any interval smaller than the big interval has a history, in the sense that it has past and/or future-tensed properties. For example, consider two non-overlapping intervals, d and e. Suppose that d is earlier than e. It then turns out that it was the case that it was not the case that d is earlier than e. This is because at one stage, d existed while e did not. It might be thought that the notion of intervals themselves as things that have histories is absurd, and that this consequence alone is enough to thoroughly discredit this version of presentism. However, the notion of intervals having past or future tensed properties does not strike me as absurd, but merely a little unkempt.
Notice also that so long as the longest temporal part of the big interval having no past tensed properties is brief enough, the problem of Kate’s history being shifted back by half the length of the big interval does not arise. This is because what exists is replaced very gradually.
Still, this second version of durational presentism faces a serious objection if it is invoked as a way of allowing presentists to be physicalists. In fact, the objection applies equally well to both versions of durational presentism.
The objection takes the form of a dilemma. Suppose that the actual world, Wa, is a presentist world with a metaphysical present long enough to enclose the conscious experience you are now having. Further suppose that the present is also brief enough to ensure that it does not enclose successive conscious experiences of yours. Now imagine another world, Wb, which is just as the actual world is except that the duration of the metaphysical present is four times longer than it actually is. In Wb, the metaphysical present is long enough to enclose successive experiences of yours. Does the presentist say that Wb is a world where there are conscious experiences? This is the dilemma.
If the answer is yes, then any reasons we might have for endorsing presentism begin to fade. After all, if the present can be durational, there is no reason at all to suppose that the metaphysical present is not long enough to encompass entire lifetimes, centuries, millennia, etc. Moreover, once we admit that the metaphysical present could be long enough for both a and b to coexist, it becomes hard to see what sort of reasons we might have for supposing that in the actual world the metaphysical present is not arbitrarily long. This sort of presentism has no apparent advantages over the tenseless view of time.
If the answer is no, then a concern is that consciousness turns out to be extrinsic in an unpalatably bizarre way. Let a be a conscious state of yours. And suppose that it will pass out of the metaphysical present to be replaced by an incompatible conscious experience, b. In Wb, however, both a and b are enclosed by the same metaphysical present. So a’s being a conscious state in Wa is constituted in part by there being nothing located at a portion of the metaphysical present earlier or later than a that otherwise has all the right features to be a conscious state. Such a restriction has little plausibility beyond a pathological desire to defend durational presentism. We might ask, for instance, how a double success could be a failure? Admittedly, this remark has no currency as an argument against the restriction (since thus construed, it clearly begs the question), but it does convey something of the incredulity with which the restriction deserves to be met.
I will mention here the only independent motivation for the restriction that I can imagine. And it is an embarrassingly poor one. a and b, as previously noted, are incompatible experiences. The usual way of understanding this incompatibility is by noting that a and b cannot be instantiated relative to the same person and same time. Thus, it is perfectly acceptable for one person to instantiate a and another to instantiate b at the same time. Likewise, it is perfectly acceptable for one person to instantiate a and b at different times. The restriction we are considering suggests that if a and b are both located in the big interval, then they must be instantiated relative to different persons. In other words, it is acceptable for a and b to both be experiences of the one person so long as those experiences never coexist. If this is the rationale, then it’s pretty clear that it must apply to any pair of incompatible properties whatsoever. And that effectively means that no qualitative change at all could occur within the big interval. This means that the only feasible version of durational presentism would be one where the times of the big interval were substantival, so that it is not big intervals that come in and out of existence, but only their contents. This leads to disaster.
First, the second version of durational presentism has it that the contents of the big interval change gradually by the accretion of new contents at one end and the loss of the oldest ones at the other. However, if it is not possible for there to be qualitative variation within a big interval, then on this view, anything that persists throughout the big interval could never change. Since, ex hypothesi, nothing can have incompatible properties at different times within the big interval, and since the contents of the big interval change only gradually, any qualitative change in a thing would usher in a big interval featuring such incompatible properties. In short, this makes qualitative change impossible. We can be pretty sure that the actual world is not like this!
Moreover, both versions of durational presentism are supposed to allow for the existence of the neural correlates of consciousness. But if neither can allow for qualitative change within the big interval then neither can do justice to the neural correlates of consciousness, which are jam-packed with qualitative change.
So either path offered by the dilemma I have presented leads the durational presentist to an unsatisfactory conclusion. I conclude that durational presentism does not, after all, help to square presentism with physicalism.
11. Craig and the Non-Metrical Present
Having argued that physicalism and presentism are at odds, I want to look briefly at a suggestion, which if correct, would mean that my arguments founder on a fundamental misunderstanding of presentism.
Presentist William Lane Craig urges that ‘There is no such thing as “the present” simpliciter: it is always “the present _____,” where the blank is usually filled by a reference to some thing or event. The duration of the present will be as long or as short as the event or thing under discussion.’ [Craig 2000: 245.]
Craig follows Prior in identifying presentness with existence. He then observes that, since it is a mode of being, ‘presentness does not involve metrical ideas.’ [246.] And this means that ‘there is no privileged unit in which temporal becoming occurs.’ [ibid.] Thus, according to Craig, the question I have been focusing on, namely, the extent of the present simpliciter, is ill-founded. Presumably, he would also say that any conclusions I have drawn from ruminating over this question are also ill-founded.
I think Craig is right, qua presentist, to identify presentness with existence. However, I don’t agree that this means the question I have been focusing on is ill-founded. I do concur that, strictly speaking, the question “How long is existence?” is a nonsensical one. But the question of the extent of the present can be sensibly phrased in terms which do not presuppose that “How long is existence?” makes sense. Here is a question for the presentist that does seem to be coherent: “What things exist, and what are the relationships that hold between them?” Of course, this is a rather broad question. However, a full answer to this question will tell us whether there exist any entities which are non-simultaneous2.
If the presentist does not like the question “How long is the metaphysical present?” because it reeks of incoherence, we can rephrase the question in terms of whether there are temporal separation relations between existing things. This question is coherent and ought to admit of an answer. If the presentist answer is yes, then in my terms, the metaphysical present has duration. Should the presentist answer ‘no’, then in my terms, the metaphysical present lacks duration.
For presentists who want to say that the metaphysical present is durationless, a more satisfactory treatment of issues surrounding the neural correlates of consciousness can be given if they embrace dualism. For dualists, conscious states are either states of non-physical entities (substance dualism) or states of physical entities, where the physical entity instantiates non-physical mental properties (property dualism).
The dualist presentist can admit that the neural correlates of your blue sky experience include a bevy of non present-tensed states of affairs, and yet deny that the experience itself has any non present-tensed constituents. This is because the neural correlates of consciousness are not identified with conscious states, but are merely correlated with them. If there is a mind/body dualism then the presentist has a means of escape from the difficulties I have presented.
The situation with respect to durational presentism is interesting. I suspect that important parts of the objection I gave against mind/body identities in the context of durational presentism could be adapted to apply also to the case of dualism. However, in terms of my current objectives it is sufficient if I have shown that presentists ought to be dualists.
Facts about the temporal properties of conscious experience are difficult to reconcile with presentism. I have argued that the only plausible way to reconcile consciousness with presentism is to endorse a mind/body dualism. To the extent that dualism is problematic so too is presentism. Of course, some presentists are dualists. In particular, presentists like Craig, who are also Christians, may not be so concerned about the conclusions drawn here.
Notice, however, that even if on balance we ought to be dualists, my arguments nevertheless undermine presentism to some degree. To the extent that we are unsure about dualism we ought also to be unsure about presentism. However, since the the tenseless theory of time is compatible with both dualism and physicalism, uncertainty about whether we ought to be dualists does not translate into uncertainty about whether we ought to be tenseless theorists.
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Augustine, Saint 1991. Confessions, Oxford.
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Bigelow, John 1996. Presentism and Properties, Philosophical Perspectives, 10: 35–52.
Braddon-Mitchell, David and Jackson, Frank 1996. Philosophy of Mind and Cognition, Oxford: Blackwell.
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Chalmers, David 1996. The Conscious Mind, New York: Oxford.
Christensen, Ferrel 1974. McTaggart’s Paradox and the Nature of Time, Philosophical Quarterly, 24 :289–99.
Christensen, Ferrel. 1976. The Source of the River of Time, Ratio, 18: 131-44.
Craig, William Lane 1997. Is Presentness a Property?, American Philosophical Quarterly 34: 27–40.
Craig, William Lane 2000. The Tensed Theory of Time: A Critical Examination, Dordrecht: Kluwer.
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See, for instance, [Prior 1970: 246–7] and [Craig 1997].
Note, however, that in some quarters it is thought that some correlates of consciousness are to be found in sub-cortical regions like the thalamus. See, for instance, [Baars and Newman 1994].
On the modularity of the cerebral cortex, see also [Thompson 1993: Ch. 8].
See [Place 1956] and [Smart 1959].
See [Braddon-Mitchell & Jackson 1996: 98–100] for an argument that functionalists should retain restricted type identities.
See [Bigelow 1996] for more details.
 [Routley 1980: Ch. 2]; [Salmon 1998]; [Hinchliff 1996].
It is probably safe to say that most presentists think that all properties (and relations) are existence-entailing. See [Prior 1967: Ch. 8], [Christensen 1976: 137], [Lloyd 1978], [Williams 1981: 109–110], [Bigelow 1996: 36–9], and [Craig 1997].
Here, I do not mean the controversial reading which takes qualia to be ineffable phenomenal items. Qualia in this sense seem incompatible with physicalism. Instead, I mean the minimal understanding according to which qualia are phenomenal ‘feels’.
This does not commit me to an extreme Cartesian position according to which, necessarily, if you believe that you are in pain then you are in pain.
You might wonder if this problem is exclusive to presentism. Suppose we modify Case 2 so that the metaphysical backdrop is one of tenseless time rather than presentism. Isn’t there still a sense in which, at t, Alan is in the process of experiencing pain? And doesn’t this fact depend on what is happening neurally to Alan later than t? If backwards causation needs to be invoked for the presentist version of this scenario, doesn’t it need to be invoked here as well? The answer to the first two questions is yes, but the answer to the third is no. The difference between the cases is that, for the tenseless theorist, being in the process of experiencing pain is a derivative property based on purely mereological considerations. Assuming as we are at the moment, that Alan can be truly said to be in the process of experiencing pain at t in Case 2 but not in Case 3, we can give the following tenseless account of being in the process of experiencing pain at t: Alan is in the process of experiencing pain at t iff Alan has a pain experience which is partially located at t.
Though this is true for the most part, there could be (very unusual) degenerate cases. Here is an example. Suppose a particular big interval encompasses a time which comprises world-state W. Further suppose that the world leaves state W but soon returns to that state, so that the following big interval includes a time which also comprises state W.
To completely avoid the worry about providing a tensed account of temporal order, it must be the case that the bits of reality that come into, and go out of, existence are not themselves intervals with proper (temporal) parts. That is, they must either be instantaneous or embody atomic intervals.
 Or, more accurately, with temporal existence. Craig wants to allow for the possibility of timeless existence [Craig 2000: 246].
For a contemporary defence of substance dualism, see [Eccles and Popper 1977]. For defences of property dualism, see [Jackson 1982] and [Chalmers 1996].
 I am grateful to John Bigelow, James Chase, Mark Colyvan, Ian Gold, Toby Handfield, John Heil, Cathy Legg, John O’Dea and two AJP referees for helpful comments and discussions. I would also like to thank the Philosophy Program at the Research School of Social Sciences, Australian National University, where some preliminary work for this paper was undertaken. I would also like to acknowledge the financial assistance of the Monash University Postgraduate Publications Award.