Geach on Time and Identity

AGAINST FOUR-DIMENSIONALISM

Quine/Lewis: time is a fourth dimension, not intrinsically different from space.

Geach: But then there really isn’t change.

Time slice 1 is P; TS2 is ~P.
Analogous to:spatial part 1 is P;SP2 is ~P.
No change on latter, so none on former.
So, time is really an illusion.

4-D Reply: Considered from the 4-D perspective, the universe is unchanging.

However, our perspective on this unchanging reality changes (Smart).

Geach: My experience changes:

I have E (I am hungry) and E* (I am full).
These are incompatible.
This is only possible if my experience changes from E to E*.

So, the 4-D view entails that there is real change, so real time, in the world.

Compare: If I think I am happy, then I am in fact happy.

Geach: perhaps we can think of minds as outside the physical world—“scrolling” along changeless reality.

Hence, mental change is not real change.

Problems:

Requires dualism.
Entails fatalism: our minds can only observe the future, can’t influence it.

Problems with temporal parts

Geach: temporal parts are distinct “objects”.

E.g., the ship-at-T1 is not identical to the ship-at-T2.

It follows that:

McTaggart-at-1901 is a distinct “object” from McTaggart-at-1921.

That’s how the following can be true:

McTaggart believed in Hegel’s dialectic in 1901 but not in 1921(according to 4-D-ism).

Geach: “believing in Hegel’s dialectic” is a property of a philosopher, not a part of a philosopher.

So, either there are two philosophers here, or A is in fact a contradiction (it attributes incompatible properties).

Both options are absurd.

Retrenching

4-D-ist: perhaps we could eliminate regular properties in favour of some that are appropriate for time slices

Geach: Time slices were introduced because of regular but incompatible properties.

Having introduced time slices, you now want to eliminate the properties you started with.
This undercuts what motivated your argument in the first place.

But can we avoid commitment to temporal slices and 4-D-ism?

Temporary intrinsics and presentism

Temporary intrinsic property: a property that an object has for a particular duration that is intrinsic to the object.

Problem: Right now I have a particular intrinsic property: I have a straight shape.

Later, I sit down. Now I have another intrinsic property: a bent shape.

But these are incompatible properties: nothing can be intrinsically both bent and straight.

Conclusion: it is impossible for me to stand up and sit down.

But we know this is false. The question is why? What’s the solution to the “problem of temporary intrinsics”?

Solutions

Solution 1: Properties are relations

E.g. shape is not an intrinsic property.
An object is not simply bent or straight
Rather, an object is bent-at-T1 and straight-at-T2
These are compatible

Solution 2: Presentism

Other times don’t exist
The only properties you have are those you have now
Nothing is both bent and straight: you are only (now) one or the other

Solution 3: Temporal parts

One temporal slice of you is intrinsically bent
Another is intrinsically straight
These are compatible

Lewis

Solution 1 entails there are no intrinsic properties (except those that persist for all time). This is surely false: red, bent, etc. are intrinsic properties.

Presentism is absurd (we’ll look at his argument shortly).

Therefore, we must accept 3 (it’s consistent with B-series anyways).

I.e.: the problem of temporary intrinsics shows us that:

Objects are 4-dimensional (with temporal parts)
B-series time is true: one can’t limit reality to just one time.

Against presentism

Lewis: The following is obviously true:

(PC) There are (at least) two different times; one at which I am bent, another at which I am straight.

But, presentism denies this: it says there is only one time (the present).

Since (PC) is true, presentism is false.

But: Why believe (PC) is true?

Lewis:

(1)We all say, “I was bent at one time, straight at another”.

(2)This ontologically commits us to the existence of non-present time. I.e., such claims are true and can only be true if more than one time exists (one at which I am S, the other at which I am B).

Paraphrase

Suppose you say:

(1)There is a dearth of Champaign in the fridge

(2)There is a way to beat Gary at chess

(3)Many different outcomes of WWII were possible

Suppose these are all true. What are the ontological commitments of (1)-(3)?

If you think (1) is true, must you believe dearths exist?
If you think (2) is true, must you believe in ways?
If (3) is true, must you believe possible events exist?

Zimmerman: No. You needn’t believe any of this. You just need to find a paraphrase of the original statements that is true (enough) to their meanings but avoids reference to troublesome entities.

For example, we can paraphrase (1) as:

(1’) There is no Champaign in the fridge

In this way, we preserve the meaning without implying that there is something in the fridge. Note: the claim is still true.

Similarly:

(2’) Gary is not a perfect chess player

In other words, one can beat him, which is what (2) claims.

(3’) Some alternate descriptions of how the war ended are consistent with how it was fought

That is, the claim is about actual descriptions, not possible events.

Misleading language

Our normal ways of talking sometimes mislead us.

We sometimes appear to commit ourselves to the existence of something when in fact we are not so committed.

We don’t have to refer to things like dearths, ways and possible events.

Zimmerman: The same applies to talk about the non-present.

The presentist thinks that talk about the future/past is literally talk about what doesn’t exist.

It is like talking about dearths or ways.

The presentist aims to paraphrase such language so that it doesn’t actually refer to the non-present.

Upshot

Zimmerman: Lewis assumes that presentism is false because we all refer to non-present times in true statements.

But he hasn’t shown that the presentist is unable to paraphrase such reference away.

Until he has shown that, his argument against presentism is not decisive.

Presentism remains one way out of the problem of temporary intrinsics.

Problem: Nobody has succeeded in such paraphrase.

Zimmerman: There are some promising approaches out there: let’s give them a chance.

Summary

An apparent dilemma:

Objects are 3-D
Objects retain their (strict) identity as they change (gain/lose parts) in time.
Leibniz’s Law

If 3, then not both (1 and 2)

Solutions:

Chisholm/Arnauld/Nicole:

2 is false – change destroys identity
Identity is a convention (overlap, etc.) adopted to relate (strictly) different 3-D objects.

Quine/Lewis/Smart:

1 is false: Objects are 4-D

They never gain/lose parts

Therefore, identity is preserved

Change = different temporal parts have different intrinsic properties.

Zimmerman/Prior:

Objects are 3-D (can’t be spread out in time)
Objects are wholly present each time they exist
They only ever have present properties.
So, incompatible properties are impossible.
As soon as P exists, ~P doesn’t exist.
This is change.
What remains identical from T1 to T2?

Relationalism: An overlooked solution?

All properties are relations (to times):

Objects are 3-D, not spread out in time.
Change = object has different relational properties (at all times).
Hence, strict identity is preserved:
O has: [(P at T1) & (~P at T2) & (Q at T3) & (~Q at T4) & …]

Strengths of this view:

Objects are 3-D
Objects survive.
Consistent with B-series (relations to different times).
Respects Leibniz’s Law:

O at all times has all the same properties.
It is always P at T1 and ~P at T2, etc.

Objections to relationalism

Geach: properties such as “P-at-T” are derivative.

Our primitive temporal concepts are “X (and Y) is (are) happening now”.
I.e., we learn about time by learning that different things can happen together, now.
Before we know this, we can’t learn to tell the time.
Other languages mark this difference more clearly—English misleads us (“at the same time” = “happening now”).

So temporal concepts like “P-at-T” are based on our understanding of “now”, and the latter can’t be replaced by the former.

Physics can’t deny this, for even physicists have to base their observations on their most basic concepts.

Compare to Broad’s view.

Paraphrase

Geach: It is easy to replace talk of events—Queen Anne’s death—with talk of objects—Queen Anne died.

Indeed, we should avoid talking about events as if they were objects.

“Queen Anne’s death” cannot name an object

It is possible to doubt whether Queen Anne died.
It is not possible to doubt whether an object.

So it is foolish to try to replace talk of people and objects with talk of collections of events.

I.e., we are not 4-D spacetime worms.

Space and time differ

Spatial terms: join names of objects.

E.g. Tom is to the left of Joe.

It seems we can do the same with temporal terms:

X and then Y.
This way it seems that “X” and “Y” name entities, events, just as “Tom” and “Joe” name objects.

Geach: this is misleading; there is a logical difference between the two cases.

We can iterate temporal clauses, but not spatial ones:
While Z (X and then Y) is logical.
Bill is between (Tom is to the left of Joe) is illogical.

Moral analogy: I can prevent someone from attending a meeting by changing its date or by locking him in a room.

Temporal barriers ≠ spatial barriers.

Conclusion

Geach’s position can be summed up as follows:

Our basic understanding of time is based on concepts such as “when”, “now”, “and then”.
These differ logically from spatial concepts.
So our basic understanding of time differs from that of space.
All investigations into the world presuppose these basic understandings.
So, it is illegitimate to conclude that time is just like space, a fourth dimension.