Your question for the next lecture!

If we had the right technology, could we fission people?!

Instead of swapping brains!

might we do something else..!

how about duplicating one hemisphere of your brain...!

and putting it into a body that’s lost its brain!

would that be a way of making two of you?!

It’s a problem with the logic of identity

Remember the case of Charles, Robert and Guy Fawkes

If Charles is identical to Guy Fawkes

Why fission poses a problem for identity

See Stanford Encyclopedia article by André Gallois: http://plato.stanford.edu/entries/identity-time/ section 5

and Guy Fawkes is identical to Robert

(which was false) then Charles is identical to Robert

Since fission means splitting into two.......

the two survivors of fission cannot be IDENTICAL with the original

consider a simpler case to start with.....

Transitivity of identity

The ship of Theseus!See the article of that title on Wikipedia

Theseus and other young men set out from Crete to Athens in a ship of 30 oars. The ship was kept by the Athenians for a long time, and they replaced planks, oars and sails as they rotted, keeping the ship in excellent condition...

Draw a space-time diagram for the ship

Launched

Very old puzzle!

All parts replaced

Finally sinks and rots away

T1

T2

Original parts preserved and rebuilt into Theseus’ ship

T3

Two ships with a common origin

ORIGIN Stages

Which ship is Theseus ship?!

Both of the candidates for identity with T1 are physically - but not functionally - continuous with it

T1

T2

T1 + T2 functions continuously as a ship while having its parts gradually replaced T3

Is it T1 (the continually repaired stage) or T1 + T2 (the continuously functioning ship) or T1 + T3 (just a pile of planks for a while) or does T1 fission into T2 and T3, like a cell dividing?

T3 may be of interest to a museum, because it contains the original parts so has historic value So T1 + T3 may be more ‘authentically’ Theseus’s ship

But once T3 is assembled from all the parts that once belonged to T1, it seems that there are RIVALS for the title ‘Theseus Ship’

Physical and psychological continuity

We could argue that there are 3 ships in this case, T1, T2 and T3

T1

T2

T3

Or we could say (loosely) that T2 is a better candidate for identity with T1 because it is BOTH physically and functionally continuous with T1

When we are dealing with people, not ships, the situation is more complex

Ships don’t remember!

A stream of direct and indirect memories can provide a kind of PSYCHOLOGICAL continuity

More strictly T2 is a better candidate for being a stage of the same ship as T1 (that is, the sum of stages T1 + T2 constitute one same ship)

Ed

Fred Ted

So what about the fission solution?

Remember the pods in The Fly, which can transport matter from one pod to another (disintegrator-integrator)

What if we can make two versions of someone in just the way a dividing cell makes two versions of itself?

Ed fissions into Fred and Ted

Fred and Ted each have Ed’s memories, hopes intentions and so on

Stream of psychological continuity

Best device is the transporter in Star Trek

it dematerializes

Two models of how it may work

and rematerializes

breaks bodies down into component molecules and shoots these through space at a great speed

makes a blueprint of an entire body, then sends the blueprint to the receiving station, while destroying the body

The teleport, teletransporter, .... makes fission VERY easy

Retains physical continuity

a new body, matching the blueprint is manufactured from a stock of molecules stored at the receiving station

destroys physical continuity No fission

Preserves psychological continuity

Makes fission possible

How can the transporter help make persons fission?

by malfunctioning or by keeping copies of the original blueprint

it might fail to destroy the original body

or it can restore the original from the blueprint it keeps

we might say, speaking loosely

that Ed can use the transporter so that there will be two of him in future, although there’s only one of him just now

but then we ask: which of these future people will be Ed?

since each of Ted and Fred are psychologically continuous with Ed

maybe Ed survives twice over

but the question of IDENTITY remains a puzzle

Ed

Fred Ted

it might “stutter” and produce two copies

Some common solutions to the duplication problem!

Ed was actually two people all along, that is, Fred and Ted shared the body called “Ed”

Ed is an earlier stage of both Fred and Ted (Ed +Fred is one person and Ed + Ted is another person)

Alternatively, Ed dies at the time the transporter destroys his body but is survived by Fred and Ted!

What does survival mean here?!

that your body dies!

but that your memories, or some things very like your memories, continue in other bodies!

Ed

Fred Ted

But are we really so independent of our bodies?

So the problem of numerical identity remains disputed!

John has the same body as Mr Smith!

John is the same person as Mr Smith when !

John has same brain as Mr Smith!

John is psychologically continuous with Mr Smith (they share the very same memories, intentions, and so forth)!

In normal cases, these three conditions all hold!

bodily continuity! psychological continuity (stream theory in Philosophy Gym)!

In abnormal cases, we find it hard to decide between!

For Locke, psychological continuity is what matters!

A view supported by Star Trek!

Copyright and references

Images and photos are those of the presenter, unless noted below

Aart Schouman, The Shoemaker, and the portraits of Guy Fawkes and John Locke are in the public domain

Image of Greek galleys from Perseus Project is in the public domain

References

The Philosophy Gym http://www.amazon.co.uk/Philosophy-Gym-Short-Adventures-Thinking/dp/0747232717

Wikipedia. The Ship of Theseus at http://en.wikipedia.org/wiki/Ship_of_Theseus

John Locke. Of Identity and Diversity at http://www.ilt.columbia.edu/publications/Projects/digitexts/locke/understanding/chapter0227.html

Eric T Olsen. Personal Identity. at http://plato.stanford.edu/entries/identity-personal/

Thanks to Norva Lo for Mr and Mrs Smith as dogs

André Gallois. Identity Over Time, sections 4 and 5. at http://plato.stanford.edu/entries/identity-time/

Thanks to Olivier for the fly from dans le jardin at http://commons.wikimedia.org/wiki/File:The_fly.jpg