2. Experience

I start from the point that consciousness – conscious experience or as I will simply say experience – exists:

This is obvious, but I'll list it as an assumption. By ‘experience’ (mass term) I mean the experiential-qualitative character or ‘what-it's-likeness’ of experiences (count noun) where this experiential-qualitative character is considered just as such, and is therefore considered wholly independently of anything else that may be supposed to be part of what experiences consist of when they're considered as a whole; and, more generally, wholly independently of anything else that may be supposed to exist when experiences exist. The relevant conception of experience and experiential content is therefore wholly ‘internalist’, in present-day terms.Footnote ²

What do I mean by ‘experience’? Basic examples will do – pain, the experience or what-it's-likeness of seeing the colour red, of tasting bananas, of finding something funny. I mean things like these. (I'll continue to append ‘or what-it's-likeness’ to ‘experience’ for the moment, although I've defined them as synonymous.) What is it to be a real realist about experience, i.e. about what-it's-likeness (pain, itching, the experience of seeing the colour red or of tasting bananas)? The best reply, perhaps, is that to be a real realist about experience is to continue to take colour experience/what-it's-likeness or taste experience/what-it's-likeness or pain experience/what-it's-likeness to be what one took it to be – knew it to be – quite unreflectively, before one did any philosophy, e.g. when one was five.Footnote ³ However many new and surprising facts real realists about experience learn from scientists – facts about the neurophysiology of experience, say, or the ‘filling-in’ that characterizes visual experience, or ‘change blindness’, or ‘inattentional blindness’Footnote ⁴ – their basic grasp of what colour experience or pain experience (etc.) is remains exactly the same as it was before they did any philosophy. It remains, in other words, correct, grounded in the fact that to have experience at all is already to know what experience is, however little one reflects about it. When it comes to experience, ‘the having is the knowing’. It's knowledge ‘by acquaintance’. To taste pineapple, in Locke's old example, is sufficient, as well as necessary, for knowing what it's like to taste pineapple.Footnote ⁵

This way of saying what I mean by ‘experience’, and hence by ‘realist about experience’, guarantees that anyone who claims not to know what I mean is being disingenuous. The last paragraph wouldn't be necessary if philosophers like Dennett hadn't looking-glassed the term ‘consciousness’ or ‘experience’.Footnote ⁶

It follows from [1] that

or that at least one subject of experience exists, because it's a necessary truth that

‘an experience is impossible without an experiencer’.Footnote ⁷ It's ‘an obvious conceptual truth that an experiencing is necessarily an experiencing by a subject of experience, and involves that subject as intimately as a branch-bending involves a branch’.Footnote ⁸ In other words: there can't be experience without a subject of experience, because

Spelt out a little: experience is a matter of experiential ‘what-it-is-likeness’ and experiential what-it-is-likeness is necessarily what-it-is-likeness for someone or something. Whatever the metaphysical nature or category of this experiencing something, its real existence can't be denied. This point is secure even if individual-substance-suggesting noun phrases like ‘an experiencer’ or ‘a subject of experience’ are somehow misleading.Footnote ⁹

I take it that [3] is a sufficient answer to those who seek to deny [2] (to claim that there can be experience without a subject), for no one can sensibly deny [3], the essential for-someone-or-something-ness of experience, and I understand the notion of the subject of experience in such a way that to say that [2] experience entails a subject of experience is simply to express [3] in a different way. One could put the point paradoxically by saying that if per impossibile there could be pain-experience without a subject of experience, mere experience without an experiencer, contrary to [2], then there'd be absolutely no point in stopping it, because no one would be suffering.Footnote ¹⁰

Another way to put the point is to say that

It's worth stating this explicitly because some like to deny [5], claiming precisely that although there obviously can't be experience without subjectivity

still there can be subjectivity without a subject – so that [2] isn't true after all.

I sympathize with the impulse behind this claim, but what it shows me is that those who endorse it are making some metaphysical assumption about what subjects are that I'm not making. Perhaps they're thinking that subjects must be things that persist for an appreciable length of time, or substances in some traditional, heavy sense of the word ‘substance’. My notion of what a subject is involves no such metaphysical commitments.Footnote ¹¹ In fact it's no more metaphysically committed than their notion of subjectivity. It rests on no more than [3], and for present purposes I can indicate its maximally non-committal metaphysical nature by saying that it has the consequence that [5] is necessarily true given that [3] is, so that [2] is secure. Given what I understand by ‘subject’, subjectivity entails a subject.

3. Materialism (Um-ism)

I'm going to restrict my attention to concrete phenomena like chairs, pains, and electrons, as opposed to abstract phenomena, like the idea of justice or the number 2 (I'm using ‘phenomenon’ as a general term for any sort of existent or candidate existent, suppressing its old meaning of ‘appearance’). I'm going to assume the truth of concretism, in fact – that

By ‘concrete phenomena’ I mean phenomena that are actually located somewhere in the universe. I take it for the purposes of argument that all location is at least temporal, if not also spatiotemporal, while noting that we may be very wrong about the nature of such location.Footnote ¹² Immaterial souls, then, and the vaguest fleeting feelings, are 100% concrete. They may seem flimsy compared with a bullet, but that's a superficial view of things. It has nothing to do with metaphysical concreteness.

I'm going to assume that monism and in particular materialism is true, i.e. that all concretely existing phenomena are physical phenomena:

which with [7] entails

The converse of [8], i.e.

is obviously true, and [8] and [10] sum to

from which I'll take it to follow that

In this discussion, then, one can always replace ‘concrete’ by ‘physical’, and conversely.

[1] and [9] entail

and I'm not just a materialist, I'm also, given [1], a ‘real’ materialist, a realistic materialist, a philosophically serious materialist, i.e. a materialist who is fully realist about the existence of (conscious) experience. Real materialism holds that experience – the concretely existing phenomenon of ‘what-it's-likeness’ considered just as such and so wholly independently of anything else – is wholly physical, although physics has no resources for characterizing its nature so considered.Footnote ¹⁵

Having declared my materialism, I should say that I take ‘material’ and ‘physical’ to be natural-kind terms; and natural-kind terms are paradigmatic examples of terms which succeed in referring to what they're introduced to refer to even though we who introduce and use them may be very wrong about the nature of what they refer to. It's plain, I think, that there's really no less reason for us to take ‘material’ and ‘physical’ to be natural-kind terms than there is for us to take terms like ‘gold’ and ‘tiger’ to be natural-kind terms. But although almost all present-day philosophers take ‘gold’ and ‘tiger’ to be natural-kind terms, very few do so in the case of ‘physical’ or ‘material’.

One reason for this, perhaps, is that we find it hard to take ‘temporal’ and ‘spatiotemporal’ to be natural-kind terms, in the way I endorsed above; and one thing then leads to another. Even if this isn't so, it's easy to see why there's so much resistance to taking ‘physical’ to be a natural-kind term. To do so is to take it to be a term that certainly refers to the reality that physics concerns itself with while allowing that we (and physics) may be very wrong about fundamental aspects of the nature of this reality. This, however, is to allow that the ultimate nature of the thing that physics is about, the physical as denoted by the natural-kind term ‘physical’, may possibly be irreducibly mental or experiential in character: not only in part, as I've already proposed, but even perhaps as a whole. Eddington and Russell are among those who suppose that the physical (natural-kind-term use) is or may be wholly mental or experiential in character, and I'm inclined to agree with them, if only for reasons of theoretical parsimony. Few, though, can stomach this consequence of taking ‘physical’ as a natural-kind term. They insist on its retaining a descriptive force that goes beyond anything warranted by physics.Footnote ¹⁶

This is understandable. To take ‘physical’ to be a natural-kind term amounts to taking it to be fully semantically equivalent to the neutral term ‘real and concrete’, so that the difference between materialism and mentalism or idealism, say, can no longer be expressed. Common terminology is further offended when it's proposed – by Russell among others – that we can know the non-structural or non-mathematically-characterizable nature of the physical only in being directly acquainted with the character of our experience (the having is the knowing). I continue to call myself a materialist in order to stress the point that my view is [i] a view about the actual nature of the concrete reality that physics deals with and [ii] a view that allows (takes it) that physics may have got a very great deal right about the (ultimate) nature of reality, but I know that this natural-kind term use of ‘physical’ isn't going to catch on. It's going to continue to be judged to be absurdly eccentric, and indeed a misuse of the word. Let me therefore introduce the term ‘um’ as a synonym for the natural-kind term use of ‘physical’. I'm an um-ist (an Ur-materialist). But I'm going to continue to use the term ‘physical’ for the most part, because the materialist or um-ist claim that matters most at present is simply the claim that experience is wholly a matter of brain activity, and until the word ‘um’ is widely used (surely it will not be long), the fact that I take physics and neurophysiology to have got a very great deal right about the brain is better kept in focus by using the word ‘physical’ than the word ‘um’.

So far, perhaps, so good. But I've spoken of objects, and said that I'm going to argue that subjects of experience are objects –

– so I need to say what an object (or ‘substance’) is. This is a very big, very general and very difficult question in metaphysics. I think we need to renounce tables and chairs as paradigm cases of objects in order to approach it (which is not to say that tables and chairs won't in the end qualify as objects).

4. Object [1]

The central thing to say, I think, is that whatever an object is, it is – I take it – a certain sort of unity

and if it's a concrete object then it is – I take it – a certain sort of concrete unity

and if it's a physical object, as it is if materialism is true, then it is – I take it – a certain sort of physical unity

Since I'm restricting my attention to the concrete (and hence the physical), I'll regularly drop the words ‘concrete’ and ‘physical’ from now on.

What kind of unity is in question? I'm going to propose that if anything is going to qualify as an object in fundamental metaphysics (by which I mean – at least – metaphysics that gives no special weight to the ordinary categories of thought), then it must be a strong unity

in a sense I'll try to illustrate. I think, in fact, that strong unity is not only necessary but also sufficient for objecthood

which sums with [17] to give

the view that unity, of a certain sort which remains to be specified, is the sole and sufficient criterion of objecthood.

I'll go on to claim that subjects of experience qualify as strong unities, and that there are in fact no better candidates for the title ‘strong unity’ than subjects of experience

I've asterisked [20] to mark the fact that it's something I want to try to explain or argue for, i.e. not something I'm [a] taking to be evident, or [b] taking to be true by definition, or [c] assuming without significant discussion, or [d] claiming to be able to derive from things in categories [a]-[c]. I can derive

from *[20] if I can make a sufficient case for [18].

Clearly I need to say more about the notion of a strong unity. Before that, though, I should say more about what I mean by ‘subject of experience’.

5. Subject

There are various different conceptions of what a subject of experience is. I'll consider three and focus on one. There is, first,

[C1] the thick conception according to which human beings and other animals considered as a whole are subjects of experience.

Secondly, there is

[C2] the traditional inner conception of the subject according to which a subject of experience properly or strictly speaking is some sort of persisting inner locus of consciousness, an inner someone, an inner mental presence.Footnote ¹⁸

Both [C1] and [C2] build in the natural assumption that a subject may and standardly does continue to exist even when it's not having any experience. For whether you think that human subjects of experience are whole human beings, or whether you think they're inner loci of consciousness, you're likely to allow that they can continue to exist during periods of complete experiencelessness, e.g. periods of dreamless sleep.

In this respect [C1] and [C2] contrast with a third conception of the subject

[C3] the thin conception of the subject according to which a subject of experience is an inner thing of some sort that exists if and only if experience exists of which it is the subject.

The thin conception of the subject stands opposed to both [C1] and [C2] precisely because they both assume something that [C3] rules out: the idea that a subject of experience can be said to exist in the absence of experience. As a materialist (um-ist) I take it that the goings on that wholly constitute the existence and experience of a thin subject consist entirely of activity in the brain.Footnote ¹⁹ A thin subject, I take it, is a certain sort of neural ‘synergy’, a neural synergy that is literally (spatiotemporally) part of the neural synergy that is an occurrence of experience – experience which is of course necessarily-subject-of-experience-involving experience.Footnote ²⁰

I face a problem of exposition, because most are so accustomed to [C1] and [C2], and to the idea that [C1] and [C2] exhaust the options, that they can't take [C3] seriously. And yet [C3] simply makes a place for a natural use of the term ‘subject’ according to which it's a necessary truth, no less, that there can't actually be a subject of experience, at any given time, unless some experience exists for it to be a subject of, at that time

which couples with [2] to give

Given the thin conception of the subject, there can no more be a subject without an experience than there can be a surface without extension. The thin conception requires that the subject be live, as it were, in order to exist at all. There is no dispositional use of the expression ‘subject of experience’.

I think it's very important to have the thin or live conception of the subject available and in play in metaphysics, and from now on I'm only going to consider the thin notion when arguing for the exemplary unity of the subject. If you think the thin conception of the subject or self is eccentric, bear in mind that it's endorsed by Descartes, Leibniz, Kant, Fichte, Nozick, and many others. Kant writes, strikingly, that ‘the thinking or the existence of the thought and the existence of my own self are one and the same’.Footnote ²¹ Hume invokes thin subjects when characterizing the notion of the subject of experience that is philosophically legitimate given his strict empiricist principles (i.e. when expounding the ‘bundle’ theory of the self): ‘when my perceptions [experiences] are remov'd for any time, as by sound sleep’, he writes, ‘so long am I insensible of myself, and may truly be said not to exist’.Footnote ²² Sprigge writes that ‘each of us, as we are at any one moment, is most essentially a momentary centre of experience or state of consciousness with the duration of the specious present’.Footnote ²³

To focus on the thin conception of the subject is not to reject the thick and traditional inner conceptions; they can all coexist. The current dominance of the thick and traditional inner conceptions does however make it important to stress that thin subjects certainly exist as defined – whatever the best view of their ultimate ontological category. They certainly exist because experience certainly exists, and to speak of a thin subject is just to speak in a certain way of a feature of reality that certainly exists given that experience exists ([2]). In fact it's to speak of a feature of reality that's an essential part of what it is for experience to exist. One can put the point by saying that experience necessarily involves experiencing (experience just is experiencing) and the existence of a thin subject is guaranteed by the fact that there's experiencing.

I suspect that the human process of experience is as a matter of empirical fact constantly interrupted, and that thin subjects are consequently short-lived in the human case, but ephemerality isn't an essential part of their definition. To believe that experience is unbroken throughout any period of wakefulness in a normal human being is to leave room for the view that thin subjects can last at least as long as human beings can stay awake. To believe that experience never ceases in a normal human being, from the first moment of experiential quickening to its final extinction, is to leave room for the view that thin subjects can last a lifetime. If we use the word ‘inner’ loosely to mean something like ‘not identical with/not the same thing as the human being considered as a whole’, and allow it to cover immaterial souls, then a Cartesian immaterial soul qualifies as a thin subject, and we make room for the view that thin subjects can last for ever.

6. Object [2]

So much for the notion of a thin subject. Now I need to go back to objects. I've proposed that there are no better candidates for being concrete objects than subjects, by which I now mean thin subjects. But are there any concrete objects? Is there any place for the notion of a concrete object or substance in fundamental metaphysics – in which I include physics?Footnote ²⁴

Some say No, e.g. proponents of radical ‘structural realism’ like the philosophers of science Ladyman, Ross, Spurrett and Collier in their recent book Every Thing Must Go. I take it that the idea is also rejected in Whitehead's ‘process philosophy’. It's an old idea, at least as old as Nāgārjuna's Fundamental Verses on the Middle Way, written about 1800 years ago. I am nevertheless going to take it to be a truth of fundamental metaphysics that

or substance, and hence that the concept of an object or substance does have legitimate application in fundamental metaphysics.

Is it also true that the concept of an object or substance has plural application in fundamental metaphysics? This is a considerably more difficult question. My inclination is to agree with Spinoza that there is properly speaking only one object or substance.Footnote ²⁵ For the purposes of argument, however, I'm going to assume that there are many. In particular, I'm going to make the ‘smallist’Footnote ²⁶ assumption that there is a plurality of fundamental physical entities (leptons and quarks, say, or ‘fields’, ‘simples’, ‘preons’, ‘loops’, ‘field quanta’, …) or as I will say ‘ultimates’

and that they can qualify as strong unities if any things do

and can therefore (given [19]) qualify as objects if any things do (and in spite of the phenomena of entanglement)

from which it follows that

I don't think [28] is obvious, when it comes to fundamental metaphysics, at least not if it is considered independently of the view that

– which might be held to be obvious, although it too is questionable, and which, with [20], entails [28].Footnote ²⁷ The truth or otherwise of [28] is a serious question in metaphysics (as indeed is the question whether there are any objects at all). I am, however, going to assume [28] for argument.

7. Interim Summary

If you've followed this far you'll know I have to do three things. I have to try to explain further what I mean by saying [17] that objects are strong unities

and equally what I have in mind in saying that all strong unities are objects

Then I have to show that (thin) subjects are strong unities

This will allow me to conclude that all (thin) subjects are objects

Might it be true not only that all (thin) subjects are objects but also that all (genuine, strong-unity) objects are subjects

With Leibniz, I suspect that [30] is also true, at least in our universe, and hence, given [20], that

is also true in our universe. This, though, is a form of panpsychism – something for another time.

One possibility at this point is to rest the idea of an object and present the argument just in terms of the idea of a (strong) unity – an idea which is perhaps clearer than, and no doubt more fundamental than, the idea of an object. I'll continue to use ‘object’, but one can if one wishes hear ‘object’ as ‘strong unity’, at the cost of putting up with a few tautologies (‘all objects are strong unities’).

8. Object [3]

The next question is this. What are the best candidates for being concrete objects, given that we want to retain the category object (or individual substance) in our fundamental ontology or metaphysics, and are committed to the view that there is more than one concrete object?

I'm going to take it in a conventional materialist way that every candidate for being an object is either an ultimate or is made up of some number of ultimates in a certain physical relation.Footnote ²⁸ A physical object, then, is either a single ultimate or a plurality of ultimates in a certain relation. Given that all single ultimates are physical objects, the remaining question is which pluralities of ultimates – if any – are physical objects? What should be our criterion?Footnote ²⁹

As before, the first and most certain thing to say about a physical object is that it is at least, and first and foremost, and essentially, some kind of unity or singularity. So the question is: given that ultimates themselves constitute unities of the right kind, which pluralities of ultimates do?

The phrase ‘some kind of unity’ is as vague as it is crucial, and some philosophers – the subjectivists – think that there are no metaphysical facts of the matter about which phenomena are objects and which aren't. On their view, whenever we judge something to be an object we implicitly or explicitly endorse an ultimately subjective principle of counting or individuation relative to which the phenomenon counts as a (single) object. I'll put this by saying that we endorse an ultimately subjective principle of objectual unity.

Can this be right? Many judgements of objecthood – many principles of objectual unity – are so natural for us that the idea they are in any sense subjective seems preposterous (nearly all of us think that cups, marbles, meerkats, jellyfish, fingers, houses, planets and molecules are individual objects, and there are clear pragmatic and evolutionary reasons why this is so). The subjectivists, however, are unimpressed. It doesn't follow from the fact that some judgements of objecthood are very natural for human beings, they say, that those judgements are objectively correct, or record metaphysical facts. If we were electron-sized, they say, our natural judgement about a stone might be that it was a mere collection of things, not itself a single object in any interesting sense.

It seems odd at first to think that merely subjective principles of objectual unity underlie our judgements that chairs and stones are objects, but it becomes increasingly natural as one moves away from such central cases. Although nearly everyone thinks a chair is a single object, not everyone does.Footnote ³⁰ Although many think cities, newspapers, galaxies, and blenders (assembled from parts) can correctly be said to be single things, quite a few do not. Although some think a body of gas is an object, many do not.

Very few think that three spoons, one in Hong Kong, one in Athens, and one in Birmingham, constitute a single thing, and yet some philosophers believe that the three spoons have as good a claim to be considered an individual object as anything else: according to one form of universalism, any plurality of ultimates in the universe, however scattered, counts as a single object in every sense in which a table does. A lepton in your amygdala, a quark in my left hand, and the ultimates that make up the rings of Saturn jointly constitute a single object just as surely as your pen or pet duck. No plurality of ultimates has a better claim to be an object than any other.

On the face of it, universalism is a wholly objectivist theory of objects. It endorses a principle of objectual unity that delivers a clear principle of counting. It tells you that if there are n ultimates in the universe then there are exactly (2ⁿ–1) objects in the universe. But it also has a highly subjectivist or ‘post-modern’ aura – it tells you that anything goes and everybody wins, that there's no real issue about whether any particular plurality of ultimates is an object or not – and it's arguable that genuinely objectivist positions emerge clearly only when more specific and limited principles of objectual unity are endorsed, e.g. by common sense, which rules in favour of tables and chairs and against the three spoons, or by Spinoza, who holds that there is only one thing or substance, the universe (‘God or Nature’), or by van Inwagen, who argues forcefully that only individual ultimates and living beings – and not, say, tables and chairs – qualify as physical objects in fundamental metaphysics.Footnote ³¹

I'm going to take it that there are at the very least various grades and types of physical unity, and that some candidates for objecthood have, objectively, a much better claim than others – given that we've committed ourselves to working with the notion of an object in our basic metaphysics. I think a human being has a better claim than your lepton + my quark + the rings of Saturn or the three spoons, given this commitment. There are vast numbers of merely ‘conventional’ unities or objects (to use Buddhist terminology) that are not of central concern in fundamental metaphysics, but there are also perhaps, certain irreducibly real objective unities, or objects.Footnote ³²

With this in place, consider the following suggestion. As one advances in genuine um-ism, deepening one's intuitive grasp of the idea that experiential, mental phenomena are physical phenomena in every sense in which non-experiential, non-mental phenomena are,Footnote ³³ one of the things that becomes apparent is this: that when it comes to deciding which phenomena in the universe count as objects and which do not, there are no good grounds for thinking that non-experiential, non-mental criteria or principles of unity – of the sort that we use to pick out a dog or a chair – are more valid than mental or experiential criteria or principles of unity. It's arguable, in fact, that there is no more indisputable unity in nature, and therefore no more indisputable physical unity or singularity, and therefore no better candidate for the title ‘physical object’, than the unity that we come upon when we consider the phenomenon of the (thin) subject of experience as it exists in the living moment of experience, experiencing seeing books and chairs and seeing them as such, say, or consciously comprehending the thought that water is wet – an event that necessarily involves the concretely occurring thought-elements water and wet forming a true unity of some sort, a unity without which the thought water is wet can't be said to have occurred at all.Footnote ³⁴ I can think of no better candidates in concrete reality for what I'm calling ‘strong’ unity, unity that is not only [17] necessary for genuine objecthood (if there is such a thing) but also – I am going to propose – [19] sufficient. As far as I can see, the only serious (and mutually excluding) competitors for equal first place are

to be identified, perhaps, with spacetime considered as a substance, and, lagging somewhat behind,

– if indeed there are any. Between these two extremes, and given the absolute centrality of unity or singularity considerations when it comes to determining objecthood, it's arguable that subjects of experience as just characterized are the best qualified plurality-of-ultimates-involving candidates there are for the status of physical objects.Footnote ³⁵

9. Fundamental Singleness

That's the idea, at any rate. The idea is to show that subjects are strong unities and therefore objects, and the subjects I have in mind are ‘thin’ subjects as they exist in the living moment of experience. Some may think that thin subjects in the living moment of experience are intolerably odd candidates for being objects. The strength of their candidacy follows from the idea that strong-unity considerations are paramount when it comes to establishing claims to objecthood in fundamental metaphysics. ‘No entity without identity’, as Quine used to say: no object without ‘identity conditions’, ‘criteria of identity’; and no concrete object, presumably, or at least no spatiotemporal object, without synchronic and diachronic identity conditions. In the synchronic case, one needs to be able to draw a line round the object – here a thin subject – in thought in such a way as to be able to say, at a given moment t ₁, ‘Here's one thin subject, and here's another’. In the diachronic case, considering thin subjects as things that may last longer than the living moment of experience, and restricting our attention to single brains for simplicity, we presumably need to be able to draw a line round them in such a way as to be able to say ‘This is one thin subject, existing from time t ₁ to time t ₂, and this, now, is another different one, existing from t ₂ to t ₃, or from t ₃ to t ₄’.

I say ‘presumably’ because I'm not sure that we do have to be able to give an account of the diachronic identity conditions of something – even in principle – in order to have reason to say that that something is an object or substance (given that we want to retain the categories of object and substance in our metaphysics). I'm not sure what I would say to someone who insisted that I could no longer claim to be dealing with the notions of object and substance at all, in abandoning the requirement of specifiable diachronic-identity conditions, but I'm going to put this question aside and restrict attention to the synchronic case.Footnote ³⁶

Consider, then, an experiencing subject at a given moment, and consider the totality of its experience at that moment. Consider its ‘total experiential field’, the total contentFootnote ³⁷ of its experiential field at a given moment, and ask whether it could fail to be experientially single or unified in being what it is.

To ask the question is to see the fundamental sense in which the answer is No. The total experiential field involves many things – rich interoceptive (somatosensory) and exteroceptive sensation, mood-and-affect-tone, deep conceptual animation, and so on. It has, standardly, a particular focus, and more or less dim peripheral areas, and it is, overall, quite extraordinarily complex in content. But it is for all that a unity, and essentially so. It is fundamentally unified, utterly indivisible, as the particular concrete phenomenon it is, simply in being, indeed, a total experiential field; or, equivalently, simply in being the content of the experience of a single subject at that moment.Footnote ³⁸ The unity or singleness of the (thin) subject of the total experiential field in the living moment of experience and the unity or singleness of the total experiential field are aspects of the same thing. They're necessarily dependent on each other even if they aren't the same thing.

I think, in fact, that there's only a conceptual distinction between them, not a real distinction, in Descartes' sense, for neither can conceivably exist without the other. In which case there's no dependence relation of a sort that requires two really (real-ly) distinct entities.

The present point, however, is independent of any dramatic metaphysical claim about the ultimate metaphysical identity of the unity of the (thin-subject) experiencer and the unity of the experiential field (or the experiential content, or, most simply, the experience). It's simply the point – the simple point – that a field, a single field, entails a subject, a single subject, and conversely. If you bring a single thin subject into existence at t ₁ then you necessarily bring a single, unified experiential field into existence at t ₁, and conversely. The singleness of the (thin) subject at t ₁ entails, and is essentially constitutive of, the singleness of its total experiential field at t ₁. So too, the singleness of the total experiential field at t ₁ entails the singleness of its subject at t ₁,Footnote ³⁹ for the material that is experienced is necessarily experienced in a single or unified experiential perspective.Footnote ⁴⁰ The point is a ‘logical’ one, as ‘trivial’ as it is important.

I'll call it Fundamental Singleness. It applies to all necessarily-subject-of-experience-involving experiential-field unities, whatever their duration, and to all possible subjects of experience, however primitive. To this extent it's independent of Kant's much higher-level claim that when we consider ourselves as subjects we must necessarily apprehend ourselves as single; his claim (in the Paralogisms section of the Critique of Pure Reason, which I will call ‘the Paralogisms’) that ‘the proposition I am simple [i.e. single] must be regarded as a direct expression of apperception’.Footnote ⁴¹ For one thing, his claim is about expressly self-conscious creatures like ourselves, whereas the present Fundamental Singleness claim doesn't depend on the subject's having any sort of express or ‘thetic’ experience of itself as subject, let alone any such experience of itself as single considered specifically as subject. If worms have experience, their experience has Fundamental Singleness, at any given time, and not just by being very simple. So does the chaotic experience of schizophrenics, considered at any given moment.

There's another respect in which Fundamental Singleness is more basic than the claims about unity for which Kant is famous. What is in question is a necessary unity of experience or experiential field that we can know to exist before we've had any distinctively Kantian thoughts about the ‘necessary unity of consciousness’ or ‘necessary synthesis of the manifold’.Footnote ⁴² It is, in other words, a necessary unity of experience that we can know to exist before we come to any aspect of the unity of experience that we can know to exist because it's a necessary condition of the possibility of other relatively complicated things that we know to exist – e.g. articulated thoughts like grass is green; or experiences that involve ‘co-consciousness’ in being at once and indissolubly both visual and olfactory and auditory; or what Kant calls ‘experience’, by which he means what some now call ‘objective experience’, i.e. experience that has, for the experiencer, the character of being experience of a world of objects existing independently of the experiencer. What is in question is a still more basic necessary unity of experience or experiential field we know to exist not by running any kind of transcendental argument of this kind but simply by considering what it is for a subject to be having any experience at all – by considering what it is for there to be an experiential point of view at all.Footnote ⁴³

I think, then, that the Fundamental Singleness point is secure, and it gives me the strong unities I need. But I'm now going to call two of my heroes – Descartes and Kant – in further support.Footnote ⁴⁴

10. Descartes on Fundamental Singleness

In the case of Descartes, a single point. When Descartes claims that the indivisibility of the mind or soul or subject is something certain,Footnote ⁴⁵ Fundamental Singleness is a key part of what he has in mind. He has been widely condemned (even mocked) for this indivisibility claim, but it's certainly correct given the central tenet of his metaphysics of mind. His conception of the mind or soul is nothing like the standard immaterialist conception of it as some sort of locus of consciousness or ‘thinking’ that isn't itself wholly constituted of consciousness or thinking. His truly radical view is that res cogitans – mind, soul – just is (necessarily subject-of-experience-involving) experience or consciousness or thinking; it has no other mode of being. This being so, the indivisibility thesis is nothing more than the assertion of Fundamental Singleness, at least so far as the synchronic case is concerned. (Kant doesn't criticize this view in the ‘Paralogisms’ section of the Critique of Pure Reason; he simply criticizes a certain metaphysical use to which it is put.)

11. Kant on Fundamental Singleness

In the ‘Transcendental Deduction’ and ‘Paralogisms’ sections of the Critique of Pure Reason Kant discusses experiential unities that are the thinking of thoughts in the narrower, cognitive, non-Cartesian sense, particular events of proposition-comprehension, e.g. judgements. We can, I propose, discern – or at least extract – the following unity argument.Footnote ⁴⁶ We know, to begin, that

We also know that

We also know that

On the present materialist (um-ist) view

We know, then, that there are actually existing physical entities that concretely realize a certain sort of unity. This (interim) conclusion is not very exciting, because the same can be said of cars or bananas.Footnote ⁴⁸ But the further point is that the concrete unity in question is a unity of a very strong sort. It's the ‘logical unity of every thought’.Footnote ⁴⁹ Cars and bananas can lose car parts or banana parts and retain their identity as the cars or bananas they are, so long as we're reasonably relaxed about the identity conditions of things. A thought, by contrast, can't lose any thought-part and retain its identity as the particular thought it is, and the same goes for a total experiential field. Every part is as essential as every other part just in being, indeed, a part. They are indivisible (and in that sense simple) unities.

If we accept this, we can infer that

What is this unity? It's the unity specified in (3), nothing more; the unity that must exist if a thought is to occur at all. It is, on the one hand, a very ordinary everyday thing, but it is also, on the other hand, something completely exceptional, because it's an absolute, concretely existing unity.

There's a further reason why it's exceptional. If we ask generally what logical or absolute unity or indivisibility might be, a first thought is that it involves perfect simplicity. On this view, if something is an absolute unity, then

The proposed absolute or logical unity of a thought such as grass is green is not like this, however, for

(the same goes, presumably, for almost any total experiential field). If this is right, then even if [U] is sufficient for absolute unity or indivisibility, it isn't necessary. One might call absolute unities/indivisibilities which fail to satisfy [U] ‘complex absolute unities’, and one might then wonder whether there can be such things. I am at present supposing that there are many of them, however mysterious they may seem considered under this description, but one might also suppose that there's only one – the universe. This, though, raises the question of the one and the many, which I don't want to consider. (The best answer to the question, perhaps, given discursive thought's limited capacity to represent the nature of reality, is that it is true that there is only one thing and true that there are many things.)

The heart of Kant's notion of logical unity is in any case simple. It is in fact the Fundamental Singleness point, adjusted to the particular case of thought. If a thought is had, if a proposition is genuinely entertained, then it's necessarily had or entertained by a single subject. In Kant's words,

And it's not only true that concretely occurring thoughts realize a certain sort of unsurpassable concrete unity. It's equally true that

As Kant observes:

I believe that these two unities are in fact and at bottom the same unity, and take it again that Kant agrees, in a passage already quoted, when he says that ‘the thinking or the existence of the thought and the existence of my own self are one and the same’. But this is a further, difficult idea. For the moment we may take it that when we have to do with these actual concrete logical or absolute unities we have to do with unities of an absolute or unsurpassable sort, unities that must count as strong unities on any account of what strong unity is.

So in knowing that such thoughts really exist, as I take it we do, and in knowing that any thought must have a certain sort of absolute unity if it is to exist at all (even though there's also a respect in which it must involve difference and complexity), we know – to put it in terms that may seem provocative to some Kantians, but shouldn't seem so to Kant, so long as he grants that thoughts really concretely exist – that there exist entities that are genuine, concrete, metaphysical unities or indivisibilities of an unsurpassable sort. (Obviously I have to drop ‘physical’ and use ‘concrete’ in order to state the point in a way Kant can accept.)

The same degree of unity exists in the case of multimodally complex sensory experiences, and a parallel argument can be constructed for the necessary singleness of the subject of any such experience.Footnote ⁵² The same degree of unity also exists in the case of experiences that are absolutely simple in content, of course – if such experiences, sensory or otherwise, are possible.Footnote ⁵³ The only difference is that in this case we lack the vivid illustration of the force of the unity that derives from the respect in which there is absolute unity in spite of complexity.Footnote ⁵⁴

Here, then, or so I propose, we move validly (i.e. without paralogism) from a ‘logical’ or ‘logico-phenomenological’ point to a substantive metaphysical conclusion. There may be neurological or cognitive-science accounts of what's going on that find astonishing complexity in these cases, many disparate and discrete events. None of this matters as long as there's a genuine, concrete experiential unity – i.e. the having of a thought, the actual occurrence of a thought. For, crucially, this unity is itself a concretely existing metaphysical unity or indivisibility of an unsurpassable sort, the unity of the concrete event of the genuine entertaining of a thought.

The phrase ‘experiential unity’ mustn't be misunderstood. There is as already remarked no requirement that the subject have any express experience of itself or its thought as a unity. The requirement is only that it have a genuine thought – that a genuine thought occur. This is the experiential unity in question, which is itself an unsurpassable, concrete metaphysical unity.

It may be granted that Kant is committed to the existence of thoughts and judgements, by his moral views if by nothing else, but objected that he can't and won't claim to know that these existent thoughts are metaphysically unsurpassable unities, if only on the grounds that they have an irreducibly temporal character, so far as we know anything about them, and so can't be known by us as they are in themselves, but only in so far as they appear to us. Against this we may bring Kant's claim that they – and their subjects – involve ‘absolute’ unity. I think that Kant would – must – on this ground be prepared to agree that they're unsurpassable unities that we can know to exist and to be such. My present aim, though, is to make a proposal, not to attempt detailed Kantian exegesis.

Kant has a very specific ad hominem purpose in the Paralogisms. His aim is to stop the [simple/single → indivisible → immaterial → incorruptible → immortal] chain of metaphysical argument that was popular in his time.Footnote ⁵⁷ In this traditional sense of ‘metaphysical’ Kant's claim is indeed, quite unequivocally, that we have no good grounds for believing that there's a real metaphysical singularity or simplicity or unity. This is his correct objection to the use that the Cartesian ‘rational psychologists’ aimed to make of Fundamental Singleness (it's not original to him). The present proposal, though, is that there's another wider sense of ‘metaphysical’ that Kant not only can but seemingly must allow, which yields a real, known metaphysical unity after all,Footnote ⁵⁸ and doesn't disrupt his argument against the rational psychologists. In this way we legitimize the Second Paralogism argument by removing the equivocation on the word ‘subject’ that renders it paralogistic: the subject that is knowably single is also knowably a metaphysically real concretely existing entity.

The proposal depends as before simply on the claim that Kant agrees that thoughts – experiences, judgements – really, concretely exist (I avoid the explicitly temporal word ‘occur’); that they are indeed metaphysically real. It goes from there to the point that he must then agree that the unity that their existence essentially involves must truly exist and be real, a genuine metaphysical unity of some sort, although it licenses absolutely no conclusions about immortality and so forth.

It may be objected that the unities in question (unity of subject, unity of thought or experience) are ‘merely functional’ unities, but it's not clear what this ‘merely’ means, as applied to concretely actualized entities (a concretely existing total experiential field, and a concretely existing subject for whom that field is an experiential field). In particular, it's not clear that it detracts in any way from these unities' claim to be true metaphysical unities. Even if we can find a sense in which they're ‘merely’ functional unities, this won't touch the fact that they're concretely existing unities, genuine metaphysical unities. And by the time we've revised and processualized the notions of object and substance in the way we have to if they're to retain any place in fundamental metaphysics, and stripped them of their claim to stand in fundamental ontological contrast with attributes or properties,Footnote ⁵⁹ we'll be in no position to hold on to any view that has the consequence that these unsurpassable thought unities or experience unities, these thinker unities and experiencer unities, have less claim to be objects or substances than paradigmatic examples of ultimates (or indeed good old fashioned immaterial minds).

We may as materialists suppose that the existence of these unsurpassable mental unities involves the existence of a large number of neurons (and a fortiori ultimates) acting in concert. In this case we may say that it essentially involves a plurality of ‘different substances acting together’, to use Kant's general formulation in his discussion of the Second Paralogism.Footnote ⁶⁰ Kant is right that we can't ground any claims about the non-materiality and hence possible simplicity or indivisibility and hence incorruptibility and hence immortality of the soul on the knowable existence of these ‘absolute’ concrete unities of subject and experiential field.Footnote ⁶¹ This, again, is the line of thought he demolishes in his discussion of the Paralogisms. This demolition is, however, wholly compatible with, and, crucially, derives its principal force from, the fact that we can know that these fundamental and unsurpassable unities exist. We can know they exist even though they're of no use in establishing the existence of a persisting immaterial subject. It's Kant himself, as remarked, who makes it most vivid that the fact that ‘the I in every act of thought is one … lies already in the very concept of thought’. He's prepared to ‘allow full objective validity’ to the ‘proposition … everything which thinks is a simple substance’, at least for the sake of argument, for his point is that even if we do this ‘we still cannot make the least use of this proposition in regard to the question of [the mind or soul's] dissimilarity from or relation to matter’ in such a way as to hope to establish immateriality and thence incorruptibility and immortality.Footnote ⁶² We can know the necessary singleness or simplicity of the subject of experience in the having of experience, but to know this is not to have ‘knowledge of the simple nature of the self as subject, such as might enable us to distinguish it from matter, as from a composite being’.Footnote ⁶³

So much for the ‘merely functional unity’ objection. It may now be objected that Fundamental Singleness is a ‘merely experiential unity’ and so not a real metaphysical unity. In one version, the objection is that the claim that the total experiential field of an experience is itself something that is a true metaphysical unity is unwarranted, because this unity is really only an appearance – because it's only from a certain point of view that the total experiential field presents as unified. In a second version the objection is aimed directly at the (thin) subject of the experience, the objection being that the unsurpassable unity of thin subject, too, is, somehow, ‘merely experiential’ or ‘subjective’, and so not ultimately real.

There's a lot to say to this, but the basic reply is simple: what's ‘merely’ about this unity? It's true that the unity of the total experiential field of an experience is essentially, and if you like ‘merely’, an internal experiential or IE unity, whatever else it is or isn't. It's true that it's a unity considered just in respect of its internal experiential character, a unity considered from the point of view of its subject, a unity that is in fact constituted as such by the existence of the point of view of its subject.Footnote ⁶⁴ It's true that there is a crucial sense in which its fundamental-unity characteristic is wholly a matter of its experiential being (when we consider the existence of the experience non-experientially, we find millions of ultimates in a certain complex state of interaction). All this is true. But it's no less true that it's an objective, ground-floor metaphysical fact that subjective experience exists and that it has the character it does. That is: the experiential fact that one of these IE unities exists is itself an objective ground-floor metaphysical fact, a fact about the world. It's a fact that stands as a fact from a perspective external to the perspective internal to the IE unity. The reason why we're right to judge an IE unity to be a fully metaphysically real unity when considering it externally, from the outside, objective point of view, is indeed nothing other than the fact that it is indeed a strong internal experiential unity, but there's nothing odd about the sense in which subjective phenomena can be objective facts. This is part of any minimally sensible realism about the subjective. All that's added here is the slightly more specific point that the existence of an IE unity that consists of the experiencing of a total experiential field by an experiencing subject at a given moment is itself an objectively existing real unity (experience is real!), both in its single-subject aspect and in its single total-experiential-field aspect (which may at bottom be the same thing). The statement that this unity exists and is wholly metaphysically real holds true outside the perspective of the subject in question, although the unity in question consists wholly of the phenomenon of the existence of that subject having that experience, with the content that it has, at the time in question.Footnote ⁶⁵