1. Identity

2. Identify of Objects  What a thing is, what makes it what it is, its properties  The problem  If an object really changes, there can't literally be one and the same thing before and after the change. However, if a changing thing literally remains one and the same thing ( i.e., retains its identity) throughout the change, then it can not really have changed. 

3. Ship of Theseus  Imagine we replace each plank of a wooden ship piece by piece, one a day, until every plank of the ship had been replaced.  Do we still have the same ship?

4. Ship of Theseus  If we have the same ship, why?  If we don’t have the same ship, why not?  We will look at three different views on how change over time can be explained.  Continuity  Similarity  Essential parts

5. Ship of Theseus  Continuity  The ship is the same if there is no break in existence.

6. Ship of Theseus  Similarity  The ship is the same if the two are similar enough.

7. Ship of Theseus  Essential Parts  The ship is the same as long as the essential parts are preserved.

8. Identity of Objects  Try with alternative cases  Take a song, change a note, now change two notes.  Is it the same song?  How many notes do you have to change before it is?  Note that even if I hum a song way off key it is recognizable as that song. (similarity rather than essential parts?)  Musicians using samples of other songs

9. Identity of Objects  If an object does not retain its identity then does it retain its other former properties?  ownership - if it's not the same car then do I still own it?  What about cases where objects seem to gain properties based on persisting through time?  squatters rights, work it long enough it's yours.  common law marriage, live together long enough and individual ownership can become joint ownership

10. Identity of Objects  Say Captain Nemo put you in command of the Nautilus and it suddenly is no longer the Nautilus, do you get in trouble?  You do seem to have lost Nemo’s ship. This is usually considered not good.

11. Identity of Objects  Change over time  if x = y then if some change in x without a change in y makes it so that x = y is false, yet that happens all the time.  For instance, if you scratch your car, then it has changed, yet we say it is the same car. How can it be the same thing, yet different?  This was part of what puzzled many of the Pre-socratics such as Anaximander, Parmenides, and Heraclitus. Parmenides went so far as to claim that there was no change, and the appearance of such change in our lives was just that, an appearance that didn't match reality.

12. Identity of Persons  Same person through time / have the same consciousness  Issues of personal identity bring us up against questions such as, "When is someone begin as a person? When does that time as a person end?"

13. Identity of Persons  Consider the three views we used to debate the identity of objects:  Contiguity  Similarity  Essential Parts  Your thoughts on which of these work for objects may well influence what you think goes for individuals too.

14. Identity of Persons  However, consider also what else might matter as far as change in the person is concerned. At the very least, two elements seem to be important:  Psychological Continuity - the person stays the same as long as their consciousness/personality has been continuous  Bodily Continuity - the person is the same so long as their bodily continuity has been protected

15. Identity of Persons  Psychological continuity gives us a theory that fits our intuitions on the possibility of having your consciousness put into another body. As long as you keep your thoughts, memories, and consciousness, you stay you, no matter how great the change in physical form has been.  Bodily continuity provides us with a way to fit intuitions that tell us that even someone who has lost all of their memory is still in some way still the same person as before.  Hence examples such as, "Here's Sarah, she lost all of her memory yesterday." If someone's psychology was the whole story about their personal identity, then a complete break with that psychology would likely mean the end of that person.

16. Identity of Persons  What parts of your personality would have to be preserved to keep your identity?  your memories?  Personality?  Brain structure? (i.e. layout of the neurons?)  Something else entirely? (consider examples from film - Total Recall, Memento)

17. Identity of Persons  Teleportation examples  reconstructing the body in another place

18. Identity of Persons  Teleportation examples  Simple case - Point A to point B, step into the box here, step out in London.

19. Identity of Persons  Teleportation examples  Point A to two points B and C - you step into the box here, and two of you step out, one in London, and one in Beijing.

20. Identity of Persons  Teleportation examples  A=B and A=C so B=C, but B does not equal C. Clearly London and China me are different, so we have a problem.

21. Identity of Persons  Teleportation examples  Could such a teleport happen (even the simple case) and you still remain you?  If so, what about the reconstruction would make you the same person?  how similar you are physically?  your memories?  The you in Beijing seems to have just as much claim to being you as the you in London, yet both of these people can't be you.

22. Identity of Persons  Ethical considerations, when can you be blamed for a past action?  If you are in fact not the same person you were five years ago, wouldn't it be wrong of me to blame you for something that person did?  If you think your future self is different than you, what is your responsibility to him or her?  Perhaps identity is irrelevant for moral responsibility  Solutions?  Psychological continuity  Identical time slices of 4 dimensional people

23. Identity of Persons  Multiple realizability  the notion that a mental state is independent of the physical realization of that mental state. This is used quite a bit in a theory called functionalism that we may look at more closely later, but for now, we use it to suggest the idea that it might not matter what a brain is made of for it to do what it does. In principle maybe any number of substances could work.  Example - silicon chip