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Time 179

But it is worth pointing out what will be another important part of the

Four-dimensionalist’s account of why we should be willing to accept the

relevant consequence of Four-dimensionalism. Any philosophical thesis

must really be thought of as part of a package, containing the thesis in

question and various associated theses. And no such package should be

evaluated just on the basis of some one, possibly counterintuitive, conse-

quence of that package. Instead, each such package must be evaluated in

terms of all of its costs and beneﬁts. And Four-dimensionalism, as it is nor-

mally defended, is a part of a bigger package (including also The B Theory,

The Tenseless Conception of Semantics, and eternalism [see below]) that

has many very impressive beneﬁts, including its elegance, its theoretical

simplicity, and its obvious consistency with leading scientiﬁc theories such

as Special relativity. So the Four-dimensionalist should say, in response to

the above argument, that accepting the existence of so many temporal

parts of the piece of chalk is a small price to pay, considering all of the

beneﬁts associated with Four-dimensionalism.

7.11 Presentism, Eternalism, and The Growing

Universe Theory

We turn now to a different controversy in the philosophy of time, one that

concerns the ontological status of non-present objects (such as Socrates

and your future great-great-grandchildren). Should we include any such

objects in our ontology? If so, should we include the future ones as well as

the past ones, or should we restrict our ontology to just past and present

objects?

The basic idea behind the view known as Presentism is that only present

things are real; indeed, on this view, the difference between the present,

on the one hand, and the past and the future, on the other hand, is “but

one facet of the great gulf that separates the real from the unreal, what is

from what is not.”

The dispute between Presentists and their rivals is analogous to a cer-

tain controversy in the metaphysics of modality between Actualists and

Modal realists. Actualism is the view that only actual objects exist. on

this view, there are no merely possible objects. Modal realism is the denial

Prior, “The Notion of the Present,” pp. 247–8.

An Introduction to Metaphysics180

of this; it is the view that some of the things that exist are not actual (they

are merely possible).

one way of capturing our temporal dispute involves talk about the

intensions and extensions of certain predicates. The intension of a predi-

cate is the concept or property picked out by that predicate. (For example,

the intension of ‘is red’ is the property redness.) The extension of a predicate,

on the other hand, is the set of things that the predicate applies to. (So the

extension of ‘is red’ is the set of all and only red things.) Two predicates that

have the same intension are said to be co-intensive (or synonymous), and

two predicates that have the same extension are said to be co- extensive.

Given this terminology, it is of course possible for two predicates that are

co-extensive to fail to be co-intensive. For example, the predicates ‘has a

heart’ and ‘has a kidney’ are co-extensive, since they apply to all of the

same things, but they are not co-intensive, since they pick out different

properties.

Now consider these two predicates: ‘is present’ and ‘exists’. Presentists

and their opponents can agree that they are not co-intensive. But the

Presentist’s opponents also say that ‘is present’ and ‘exists’ are not

co- extensive. For the Presentist’s opponents think that ‘exists’ applies

to some things that ‘is present’ does not apply to, such as Socrates, for

example, and (perhaps) your future great-great-grandchildren.

The

Presentist, on the other hand, says that ‘is present’ and ‘exists’ are (always

and necessarily) co-extensive. Whatever ‘exists’ applies to, according to

the Presentist, ‘is present’ also applies to.

So one way of capturing the issue is as a controversy over whether

these expressions – ‘is present’ and ‘exists’ – are necessarily and always

co- extensive. Here is another way of capturing the dispute. let our quanti-

ﬁers be completely unrestricted, so that they range over absolutely every-

thing that there is. Then we can ask whether the following sentence is

always true.

(P) everything that exists is present.

or, we can ask, is the following sentence sometimes true instead?

Note: some Non-Presentists prefer to say that non-present objects exist, without

existing now, where ‘x exists now’ is taken to be just another way of saying that x is

present.

Time 181

(NP) Some things that exist are non-present.

Here are our ofﬁcial formulations of the relevant views:

Presentism

only present objects are real.

Eternalism

Past objects, present objects, and future objects are all equally real.

The Growing Universe Theory

Past objects and present objects are real, but future objects are not.

It is often said that Presentism is the common-sense view. But there

are some rather glaring problems facing the Presentist. one such prob-

lem is that the view seems to lead to the conclusion that nothing at all

really exists. After all, the present is razor-thin; it is vanishingly small.

In fact, the present seems to have zero temporal extension. So it seems

like the Presentist’s ontology contains nothing. And that is certainly

problematic.

Another worry facing the Presentist has to do with singular propos-

itions about non-present objects. For here is a sentence that will strike the

man on the street as clearly true:

(1) Socrates was a philosopher.

And yet (1) appears to express a ‘singular proposition’ about Socrates, i.e., a

proposition speciﬁcally about Socrates, and one that contains Socrates (the

man himself) as a constituent. But it looks like the existence (not to men-

tion the truth) right now of a singular proposition about Socrates entails

the existence of Socrates.

A third worry about Presentism has to do with relations between pre-

sent and non-present objects. Isn’t it true, for example, that John admires

Socrates? And isn’t it true that Ned stands in the son of relation to his

father, despite the fact that Ned’s father is no longer present? Moreover,

don’t these apparent truths commit us to saying that present objects can

stand in various relations to non-present objects?

For an example of a defense of Presentism see Prior, “The Notion of the Present” and

“Some Free Thinking about Time;” and Markosian, “A defense of Presentism.”

For an example of a defense of eternalism see Sider, Four-Dimensionalism.

For an example of a defense of The Growing Universe Theory see McCall, A Model of

the Universe.

An Introduction to Metaphysics182

These apparent truths certainly seem to commit us to saying precisely

that. But it looks like the Presentist has to deny that any present object

can stand in any relation to any non-present object. And so it looks like

the Presentist has to deny that John really stands in the admiring relation

to Socrates or that Ned really stands in the son of relation to his father.

And if these really are consequences of Presentism then they are certainly

strange and troubling commitments of that theory.

A fourth worry about Presentism has to do with non-present times,

such as the time of your birth and the time of your death. We certainly

seem to talk about such times. But how can we do that if they don’t

exist?

There is more. Presentism is a special version of The A Theory. (For it

doesn’t make sense to say that only present objects exist unless you also

say that presentness is a genuine, monadic property.) So any argument

against The A Theory (such as McTaggart’s argument, the argument from

relativity, and the rate of passage argument) will also be an argument

against Presentism.

The eternalist faces none of the problems just mentioned in connec-

tion with Presentism. But what about The Growing Universe Theory?

Well, it should be clear that proponents of The Growing Universe Theory

will avoid the hardest versions of at least some of the problems facing

Presentism. For example, proponents of The Growing Universe Theory

need not worry about the accusation that they have a razor-thin ontol-

ogy, since their ontology is plenty thick (and growing all the time!). Nor

do they have to worry about singular propositions about past objects

like Socrates, since they have such objects (and hence singular propos-

itions about them) in their ontology. And as for the question of singular

propositions about future objects (like your great-great-grandchildren),

well, it is much more plausible to say that there really are no such sin-

gular propositions than it is to say the same thing with respect to past

objects.

Similarly for the problem of relations between present and non-present

objects: proponents of The Growing Universe Theory have all the past

objects they could want for present objects to stand in relations to; and it

is much more plausible to deny that present objects stand in relations to

future objects than it is to deny that we stand in relations to past objects.

Time 183

But some of the problems facing Presentism will translate into prob-

lems for The Growing Universe Theory. For example, proponents of The

Growing Universe Theory still face the problem of how we manage to talk

and think about future times, if they don’t really exist. And since The

Growing Universe Theory is, like Presentism, a version of The A Theory,

the Growing Universe theorist must still have a response to all of the argu-

ments against The A Theory.

7.12 Is time like space?

It may be that there are available to the Presentist (and to the proponent

of The Growing Universe Theory) plausible solutions to all of the above

problems.

Then again, it may be that there are not. But in any case, we

are inclined to think that the best responses to most of the above difﬁ-

culties on the part of the Presentist (or the proponent of The Growing

Universe Theory) will involve some appeal to the controversial claim that

time is fundamentally different from the dimensions of space. And if we

are right about that, then the debate between Presentists and proponents

of The Growing Universe Theory, on the one hand, and eternalists, on the

other hand, can best be seen as part of a larger debate within the philoso-

phy of time over the extent to which time is similar to the dimensions of

space. In this larger debate we can include, on the side of those who say

that time is like space, B Theorists, proponents of Four-dimensionalism,

and eternalists. And on the side of those who say that time is crucially

different from space we can place A Theorists, proponents of Three-

dimensionalism, and those who endorse either Presentism or The Growing

Universe Theory.

For detailed attempts to solve these and other problems facing Presentism, see

Markosian, “A defense of Presentism.”

184

8 Material objects

8.1 A statue and a lump

Suppose that on Monday you bring home a lump of clay and place it on

your workbench. Then on Tuesday morning you carefully fashion the clay

into a beautiful statue of a snowy owl, which remains in your workshop

for all your friends to admire when they come over that night. But suppose

that on Wednesday you wake up in a bad mood and decide that you don’t

like the snowy owl after all. So that morning you squash it back into an

amorphous lump of clay.

This example raises several interesting metaphysical questions. Chief

among them is this: how many objects are there on your workbench on

Tuesday night? one plausible answer is that there is just one object there,

namely, the statue. After all, most people, if asked to count the objects on

the workbench at that time (most people without a metaphysical agenda,

that is), would examine the situation and conﬁdently say that there is just

the statue there on the workbench.

Although “one” might seem like the common-sense answer to our

question about how many objects are on the workbench on Tuesday

night, there are also some good reasons to think that the right answer

is “two.” For it is natural to think that there is the lump of clay, which

is one thing, and also the statue, which is something distinct from the

lump. one reason for thinking this is that the statue and the lump have

different histories. After all, the lump was brought home on Monday,

when the statue didn’t yet exist, and the statue came into existence on

Tuesday morning, when the lump had already been around for quite a

while. Also, the statue went out of existence on Wednesday morning,

when you squashed it, but the lump of clay continued to exist for a long

time after that.

Material objects 185

We will return later in this chapter to the question of whether the

statue and the lump are two distinct objects, but in the meantime suppose

that on Tuesday night one of your friends points out that, even if the statue

and the lump are one object (rather than two), the number of objects on

the workbench is still many more than one. For there are in any case all

of the molecules, atoms, and subatomic particles that compose the lump

of clay. In fact, the number of subatomic particles alone, as your friend

points out, is likely to have more than twenty digits in it. That’s a big num-

ber, even without counting all of the atoms and molecules (not to mention

the lump and the statue).

Suppose another friend argues that there are indeed a large number of

objects on the workbench, but not quite as many as the ﬁrst friend is sug-

gesting. For, according to this other friend, all that really exists on your

workbench is a swarming mass of subatomic particles. Any other putative

objects, she says, including any alleged statue, lump, molecules, and atoms,

are mere ﬁctions – useful ways of talking about the many swarming par-

ticles. The ultimate reality, she insists, consists of just the fundamental

particles.

Are the statue and the lump of clay two distinct objects? Is there even

a statue or a lump on the workbench? Are there such objects as atoms

and molecules, or does the physical world consist entirely of fundamental

particles? These are some of the questions about material objects that we

will be concerned with in this chapter. others include questions about

the circumstances under which two or more objects compose a further

object, when an object has no parts, whether an object can gain and lose

parts, and the relation between a physical object and the matter that it

is made of. But our ﬁrst question is even more basic than that. For we

begin with the question of how to distinguish between physical and non-

physical objects.

8.2 Physical and non-physical objects

We are interested in this chapter in a number of questions about physical

(or material) objects. That’s one main reason to want to be able to distin-

guish between physical and non-physical objects. Another main reason

has to do with the role this distinction plays in many areas of philosophy,

An Introduction to Metaphysics186

including The Mind–Body Problem and discussions of various forms of

materialism.

So what exactly are physical objects?

George Berkeley said (roughly) that physical objects are the things out-

side of our minds that can be sensed.

(He also ended up arguing that

there can be no such things, but his arguments for that conclusion can be

divorced from his account of physical objects.)

one difﬁculty with Berkeley’s sensational account of physical objects

is that different beings have different sensory abilities, which means that

this account threatens to make the notion of a physical object a relativis-

tic one. That would be a highly undesirable result, given the crucial role

played by the concept in various philosophical debates. In order to avoid

this result, then, we could modify the sensational account to say that

physical objects are objects that can be sensed by some sentient being

or other. But if we say this then we run the risk of casting our net much

too wide; for it may be possible for a disembodied mind to sense another

such mind, and it may also be possible for an extremely sensitive creature

to sense such seemingly non-physical entities as propositions. And there

is also this objection to the sensational account: it turns the property of

being a physical object into an extrinsic property of the things that have

it; and yet, intuitively, being physical is an intrinsic property of physical

objects.

An alternative account of the physical holds that physical objects are

the objects studied by physics.

This appears to be a popular approach,

especially among philosophers writing on physicalism. But it leads very

quickly to a deﬁnitional circle if, as we suspect, the best deﬁnition of

‘physics’ is the study of physical objects.

In addition, there are a number of apparent counterexamples to the

physical theory account of physical objects: numbers, equations, formulas,

functions, properties, and propositions all seem to be among the objects

studied by physics, but none of them strikes us as a physical object. Also,

it is quite possible that some day it will turn out that the best physical the-

ory is one that (correctly, we can suppose) posits ghosts and goddesses and

other entities that we would not want to call physical objects.

Chapter 6 discusses several versions of materialism. our focus in that chapter was the

nature of mental states.

See Berkeley, A Treatise Concerning the Principles of Human Knowledge, Part I, section 4.

See, for example, Smart, Our Place in the Universe, p. 79.

Material objects 187

W. V. o. Quine has suggested that a physical object is “the aggre-

gate material content of any portion of space-time, however ragged and

discontinuous.”

on the face of it, this proposal looks circular, since we

are taking ‘material’ to be synonymous with ‘physical’. But it may be pos-

sible to avoid this problem simply by subtracting the word ‘material’ from

Quine’s suggestion, leaving us with a proposal according to which a phys-

ical object is the content of any portion of space-time.

This proposal has some plausible consequences, but it also comes with

some noteworthy metaphysical baggage. For this Quinean account entails

a thesis called Universalism (see below), according to which (roughly) for

any group of objects, there is a further object whose parts are the mem-

bers of that group. Thus, for example, according to Universalism, there is

an object whose parts are your head, the president’s shoes, and a single

quark from the surface of the moon. As we will see in 8.8 below, there are

some interesting arguments in support of Universalism; but it is neverthe-

less a highly controversial thesis. Thus, the fact that our Quinean account

of physical objects entails Universalism counts as a signiﬁcant cost of that

account.

A further problem for the Quinean view is that it may prove impossible,

on that view, to distinguish between a particular physical object, such as a

ball, say, and any event that is spatio-temporally coincident with that ball,

such as the ball’s history. What’s more, on certain theories of universals, it

may also prove impossible to distinguish between the ball and its various

life-long properties. (Perhaps this problem is the reason Quine included

the word ‘material’ in his statement of the view in the ﬁrst place.)

Peter van Inwagen has suggested an alternative account of physical

objects.

According to van Inwagen, there is a certain family of proper-

ties – such as being located in space, having spatial extension, persisting

through time, being able to move about in space, having a surface, hav-

ing mass, being made of matter, and so on – that are associated with the

concept of a physical object. Van Inwagen further suggests that the latter

concept is an imprecise one, and that the extent to which an object exem-

pliﬁes all or most of the concepts on the associated list is the extent to

which that object is a physical object.

Quine, “Whither Physical objects?,” p. 497.

van Inwagen, Material Beings, p. 17.

An Introduction to Metaphysics188

This common-sense account of physical objects may well be an adequate

way of capturing the everyday notion of a physical object. But when it

comes to the concept of a physical object that is featured in the disputes

of philosophers, the common-sense account is problematic. one difﬁculty

is that it makes the concept of a physical object a vague one, which is

undesirable given the role that concept plays in numerous philosophical

disputes.

Another problem for the common-sense account is that it entails that

quarks, electrons, atoms, and even certain large organic molecules may

not be physical objects.

This is bad for two reasons. First, since quarks,

electrons, and so forth are all among the parts of macroscopic physical

objects, this consequence of the common-sense account goes against the

very plausible thesis that a physical object cannot have a non-physical

object among its parts. And second, no one on either side of the debate

over physicalism thinks that the existence of quarks and electrons refutes

physicalism.

There may be another problem facing the common-sense account of

physical objects. Imagine a possible world with very different properties

and laws of nature from those in the actual world. Suppose that in this

other possible world, there are point-sized objects with spatial locations

that never persist through time but, instead, pop in and out of existence

instantaneously. Since they don’t persist, these objects of course don’t

move around. Suppose further that they don’t have mass, or any of the

other familiar properties of physical objects in this world, but instead

exemplify various alien properties that nothing in the actual world ever

exhibits; and suppose ﬁnally that it is these strange, alien properties that

ﬁgure in the laws of nature governing this other possible world. The pro-

ponent of the common-sense account has to say that there are no physical

objects in such a world (since the objects in question have almost none of

the properties on the relevant list); but this seems like a strange result. For

For as van Inwagen himself says, “one has to be very careful in ascribing any of the

features in the above list to such things; and talk about the surfaces of submicro-

scopic objects, or about the stuffs they are made of, tends to verge on nonsense”

(Material Beings, p. 17). It should be noted, however, that van Inwagen considers it a

feature of his view, rather than a bug, that it seems to entail that quarks, etc., are not

material objects.