PY3701 – Persistence
Intuitively, things change over time; the Sun, you, a dog, whatever.
When an object changes, it changes either with respect to its properties or its parts.
An object O, changes with regard to property P, iff O has the property P at one time and at a
later time, O does not have P.
An object O, changes with regard its part P, iff O has the part P at one time and at a later
time, O does not have P.
Leibniz was a supporter of the theory of mereological identity (MTI) – which itself supports the
belief that an object cannot persist through a change of parts. For any compound objects, x and y, x
= y only if every part of x is a part of y, and every part of y is a part of x. I.e., an object continues to
exist (from time T1 to time T2) only if it is composed of all the same components at T2 as it was
composed of at T1. Sameness of parts is a necessary condition of identity.
The ship of Theseus example:
The ship S1 leaves the harbour, and sheds all its parts, rebuilding itself with new parts. The ship that
pulls into harbour, S2, and the ship that was built with the old components, S3, come back together
and park alongside one another.
It is obvious that S2 ≠ S3.
1. The MTI states that because every part of S1 is a part of S3, and every part of S3 is a part of
S1, then S3 = S1, and S2 is a new ship.
2. The alternative is to abandon MTI and hold that S1 = S2. On this account, we still have two
ships, but their identity and non-identity relations are different: one ship (S1) was sailed out
by Theseus and (S2) sailed by the same people, and another one (S3) was created (out of
used parts) during the voyage and was sailed into port by the Scavenger.
However, both of these result in unintuitive answers.
1. The problem with 1 is that it requires that S2 have the captain change ships to S3. However,
the MTI can be preserved if we disregard this specific example – if we assume that no
people are to be considered in the example, then the people-less ships are indeed identical.
● A greater problem is that if this argument works, then any property that has changed at any
point from the way it was, means it no longer exists, and there is a new thing in its place.
Common sense alone defies this – i.e. If but one plank on the ship had been replaced, would
it be a different ship? Many philosophers would say of course not, however, the ship that
has been floating on the seas for a few years does have different properties from the original,
as does a desk that's taken a pounding from hundreds of people carving their names in it or a
tree that's lost some of its leaves... but under the MTI, all these objects would be
● The MTI can be saved, however, by applying a perdurantist's view; applying particular
properties to particular times, i.e., they are indexed to times (temporally indexed) For
example, S1 has M1 at T1 – if we say that the ship has the mast, then the property of having
the mast is indexed to that time. The same obviously applies for S2 – we can say that S2 has
M2 at T2, or had M1 at T1. Because under the MTI, ―change‖ is defined as something
having one property at one time and not at some other time, it would appear that any given
object has all the properties throughout time. Because S1 and S2 have the same temporally
indexed properties, they would be the same ship.
2. The problem with 2 is that in holding that S1 = S2 and admitting (as it must) that S2 S3 ,
it must also hold that S1 S3. Yet every part of S1 is a part of S3, and every part of S3 is a
part of S1... So S1 and S3 are two different ships even though their parts are the same; and
S1 and S2 have no parts in common, and yet are the same ship (again, if we disregard the
human aspect and perhaps find a different example, the MTI holds more weight)
But I think we can conclude that the MTI is too strong. It denies identity to objects that we think of
as persisting through time, like the majority of living creatures (trees lose leaves, animals moult,etc)
Everything there is, is present. No object is located at any other time than the present. So, Being
located at multiple times is a necessary condition for persisting. If the present is extended, it must
have separate parts - but these must be simultaneous if they are truly part of the present.
―the only statements ascribing qualities to objects that can strictly be true are those that
ascribe those qualities now, to objects that exist now”.
So from this we can infer that the only strictly true statements of the form:
‗a is F at t‘ [where a is an object, F is a quality, and t is a time]
are ones of the form ‗a is F now‘‖ (Lowe 42-3).
Given that it is true, presentism solves the problem of qualitative change in this way:
―it follows that it is simply never strictly true to say that one and the same object possesses
mutually incompatible qualities at different times, since the only real time is the present‖
Problem with presentism: If presentism is true, how are we to make sense of
normal conversations about past and future times? It would be about supposedly impossible
And if we adopt a scientific stance: Assume we have a list of all the possible events that are
occuring at this, and only this point in time. The list says ―the dog dies at this instant‖ - but
when one considers that it takes time for the light from the dog to reach your eyes, you are
already viewing the past. This is even more obvious when one considers astronomical
events, some of which occurred billions of years ago, and we're only now just seeing.
Everything you see occurred, to a greater or lesser degree, in the past.
This leaves Endurantism and Perdurantism.
Endurantists hold that objects are three-dimensional, have only spatial parts, and wholly
exist at each moment of their existence. Endurantists agree with perdurantists that persisting
objects are located at multiple times. However, they reject the further claim that persisting
objects have distinct proper parts at each time at which they are located. According to
endurantism, at least some persisting objects are wholly located at each of multiple times.
An object that persists in this way is said to ―endure‖.
● There is a distinction between saying that;
an object is wholly located somewhere, and saying that it is singly located somewhere.
To say that x is wholly located at t is to say that x is located at t, and there is no proper
part of x that is located outside t.
To say that x is singly located at t is to say that x is located at t, and there is no region
outside t at which x is located.
● According to endurantism, these two come apart for enduring objects. An enduring object
may be located at t1 and t2, without having a part located at t1 and not at t2, or a part
located at t2 and not at t1. Enduring objects have no proper temporal parts.
An argument against Endurantism:
Lewis argues that this is inconsistent with the idea that objects undergo real change. If the very
same object can be both F at one time, and not F at another, this means that F-ness must be a
relation to a time, but this means that it is not an intrinsic property. So any property that an object
can change must be extrinsic, so nothing undergoes real change.
Endurantism says that things are substances that remain identical despite changes in their parts and
properties. According to the endurantist, persistence is identity through time. Endurantism has these
(1) asymmetry between time and space;
(2) problems with change of properties;
(3) problems with changes of parts;
(4) problems with fission; and
(5) problems defining different kinds of persistence conditions for different kinds of things.
Attempts to fix endurantism only make it worse. Endurantism is false.
Says that objects persist by having different temporal parts at different times.
■ that objects are four-dimensional,
■ have temporal parts,
■ and only partly exist at each moment of their existence.
■ Every persisting object is located at multiple times, having a distinct, proper part located at
each time where the persisting object is located.
● Spatial parts of an object are located at some, but not all, of the points/places at
which an object is located.
● Temporal parts are located at some, but not all, of the times at which an object is
Spatio-temporal continuity Theory (STC)
A persisting object must trace a continuous path through space-time. And tracing a continuous path
is compatible with a change of parts, so long as the change is gradual and the form or shape of the
object is preserved through the changes of its component materials. This view is consistent with the
aformentioned example of Ship S1 ending up as ship S2.
Problems with STC
Consider that an object can be disassembled and then reassembled – (for example, a bicycle that is
taken apart. The parts are then placed in a number of separate boxes, which are then shipped,
separately, across country. The boxes are then unpacked and the bicycle is reassembled.) How do
we account for its identity? STC breaks down in this case, for there is no continuously existing
bicycle-shaped object tracing a smooth path through space-time. But MTI gives us the right result:
the reassembled bicycle is made of exactly the same parts as the one that was taken apart, and so is
numerically the same bicycle.
In fact, there is a way of describing the case of Theseus‘s ship that seems to demand MTI rather
than STC. Suppose the ship A is in a museum, and a clever ring of thieves is trying to steal the ship
by removing its pieces one at a time and then reassembling them. Each day, the thieves remove
another piece, and replace it with a look-alike. When they have removed all the original pieces, we
are left with this situation. There is a ship, B, that is in the museum (made of all new materials), and
there is a ship, C, in the possession of the thieves (the original pieces of A now reassembled).
Which ship is A (Theseus‘s original ship)? Surely not B—it‘s just a copy of A, left behind in the
museum by the crooks to cover up their crime. It is C that will interest the antique dealer who is
interested in buying A, the original ship. If we compare this argument to the original case of the
ship, it makes the MTI look to be more likely.
The exam question from last year, broken down:
Assume that the desk in front of you has undergone some small physical changes
since the start of the examination.
1. Is it literally the same object that was there when you entered the room?
2. If so, what would have to happen in order for it to cease to exist?
3. Moreover, if it is the same desk then how can it now have different properties
and yet be the same thing?
4. If it is not the same object then what is it, and what happened to the original
Part (1): a problem concerning how change is possible. Hypothetically, the desk in front of you was
painted cleanly this morning (for the sake of not being annoying, let's assume that the paint is part
of the table). Having sat down, and hammered away at the surface with a pen until all the varnish
But nothing can be both painted and damaged. Of course, it's the fact that the table is painted and
damaged at different times which saves it from metaphysical peril; that is obvious.
So what is it about the passage of time which makes it possible for one and the same object to have
apparently incompatible properties?
If the table has temporal parts, this explains how it can change: an earlier temporal part of the table
is painted, while a later temporal part of the table is damaged. More grandly: an earlier temporal
part has the property being-painted, while a later temporal part has the property being-damaged.
The same can apply to anything – you can have a hot head and cold feet, thus be hot and cold at the
same time; It's obvious that that different parts of the same object can have different properties.
One objection is that perdurance-style temporal variation is not really change at all: the whole four-
dimensional table is neither painted nor damaged, so can't change between these states, and the
temporal parts are either permanently painted or permanently damaged, so they don't change either.
In response, perdurantists distinguish two ways of talking about persisting things - an atemporal
way, which takes in all times at once, and a temporal way, relative to various times.
On the atemporal way of talking, the whole four-dimensional table is neither painted nor damaged;
nevertheless, it's true to say in temporal terms that the whole table is painted at 9am, and the whole
table is damaged at 12:30pm, because of the properties of the relevant temporal parts.
Stage theorists give the same basic account of change as perdurantists do, but they have a slightly
different response to the no-change objection. According to perdurantists, talk about the same table
at different times is straightforwardly made true by one and the same four-dimensional object
existing at different times.
● For a perdurantist, it is tricky to explain what it is for that object to be damaged right now:
It is for it to have an damaged temporal part right now.
● In contrast, according to stage theorists, talk about the table being damaged right now is
straightforwardly made true by the table being damaged, since the table just is a momentary
stage which exists right now.
● it is for the current momentary table to stand in certain intimate causal relations to
momentary tables in the past and the future.
(2) asks: If [the table is the same as when you came in], what would have to happen in
order for it to cease to exist?
If we assume the mereological theory of identity to be true, we can claim that a
change in any part of the table's structure, or any property change would cause the
table (T1) to no longer exist, and would become a different table. (finish this later)
(3) asks: ―Moreover, if it is the same desk then how can it now have different properties and
yet be the same thing?” Rewritten: How can one and the same thing have different properties at
● The presentist's view could give an answer that seems to dissolve the problem of change:
Since only the damaged table is present, its painted state does not exist, so there's nothing to
worry about. i.e., it doesn't have different properties, it's just the thing that it is, in 'the now'.
● Endurantists may claim that objects change by standing in different relations to different
times. There is no absolute fact of the matter regarding the damagedness of the table:
instead, the table bears the being-painted-on relation to Monday, and the being-damaged-on
relation to Friday.
● (Alternatively, perhaps the table possesses two compatible properties, being-painted-on-
Monday, and being-damaged-on-Friday.) As previously stated, it's quite possible for an
object to bear apparently incompatible relations to different things: you are bigger than an
ant, and smaller than the statue of liberty, but metaphysicians don't puzzle over how you can
be both bigger-than and smaller-than. However, those who oppose this relational view of
changeable properties claim that it's just too relational - the table seems to lose all its
intrinsic nature. We may also worry that, as with the temporal parts account, it's not clear
whether anything really changes on this picture: the table always stands in the same
relations to the various times.
(4) asks: If it is not the same object then what is it, and what happened to the original desk?