Survival and Identity

1. Survival and Identity David Lewis’s Response To Parfit

2. Rehearsing Parfit Neo-Lockeanism:What matters for survival is psychological continuity/connectedness

3. Lewis Defends Neo-Lockeanism • What matters for survival is mental continuity and connectedness • These are relations between total psychological states that occur at stages that exist at different times such that: • Change (difference in states) is gradual rather than sudden • Changes are a result of the lawful causal dependence of one state on another • Mental continuity and connectness are relations between (momentary) stages that are temporal parts of persons; personal identity is a relation between the extended 4-dimensional ‘worms’ of which they are parts.

4. Neo-Lockeanism: Pro and Con Arguments Parfit: For Neo-Lockeanism • If our criterion for personal identity is psychological then identity isn’t what matters for survival. • Our criterion for personal identity is psychological. • Therefore, identity is not what matters for survival. Against Neo-Lockeanism • If our criterion for personal identity is psychological then identity isn’t what matters for survival. • Identity is what matters for survival. • Therefore, our criterion for personal identity is not psychological

5. One Persons Modus Ponens is another’s Modus Tollens If a job is worth doing, it’s worth doing well. Modus Tollens Modus Ponens

6. The R-relation and the I-Relation Surviving and being the same person

7. Identity and Survival • Parfit argues that what matters in survival is either identity or mental continuity/connectedness; that these two things cannot both be what matters in survival and that what matters in survival is not identity. • Contra Parfit, Lewis contends that the opposition is a false one, since it obscures the fact that mental continuity and connectedness is a relation between two person‐stages whereas identity is a relation between temporally extended ‘continuant persons’ with stages at different times. • The postscript includes both Lewis’ rejoinder to Parfit's objections, as well as a further defense of his own account

8. Personal Survival • What matters in survival is mental continuity and connectedness: ‘what I mostly want…is that my mental life should flow on.’ • Similarity: change should be gradual rather than sudden. • Lawful causal dependence: lawful regularities concerning the the successions of mental states, as exemplified in everyday cases. • Psychological continuity transitive; connectedness is not • Connectedness: direct relations of similarlity and causal dependence between psychological states • Continuity: ‘step-by-step paths from here to there’

9. Identity and R-Relatedness • We have a discrepancy of formal character between identity and any suitable relation of mental continuity and connectedness. • He who says that what matters in survival is a relation of mental continuity and connectedness is speaking of a relation among more or less momentary person-stages, or time-slices of continuant persons, or persons-at-times. • He who says that what matters in survival is identity…[is] speaking of identity among temporally extended continuant persons with stages at different times. • It is pointless to compare the formal character of identity with the formal character of the relation that matters in survival.

10. The Relation Between Tail and Trunk • Is not identity but… • The spatial unity relation for elephant • Spatio-temporal continuity • Causal connectedness in one organized system

11. Relation Person-Stages at Different Times • Not identity • The temporal unity relation for person. • Spatio-temporal continuity (to underwrite causal continuity) • Psychological continuity/connectedness

12. The R-Relation and the I-Relation • R-Relation: the psychological relation on person-stages that matters in survival. • I-Relation: the relation that holds between the several stages of a continuant person. • Continuant Person: a maximal I-interrelated aggregate of person-stages • Each stage of which is I-related to every other stage of the person and • The person is not part of any larger I-interrelated aggregate • Claim: Something is a continuant person iff it is a maximal R-related aggregate, i.e. the I-relation is the R-relation: that is to say, identity is what matters.

13. So why distinguish R- and I-Relations? • Because we went to put the question of whether the R-relation can be criterial for personal identity • Comparing the R-relation with identity won’t work because personal identity doesn’t hold on person-stages. • The I-relation by definition holds on stages of the same person since it’s defined as the relation that holds on a pair of stages if and only if they’re temporal parts of the same person • So the question of whether holding psychological connectedness/continuity is what matters is compatible with holding that identity is what matters is the question of whether the R-relation is the I-relation.

14. The I-Relation may be one-many ‘It would be wrong to read my definition of the I‐relation as saying that person‐stages S1 and S2 are I‐related if and only if the continuant person of whom S1 is a stage and the continuant person of whom S2 is a stage are identical. The definite articles require the presupposition that I have just questioned. We should substitute the indefinite article: S1 and S2 are I‐related if and only if a continuant person of whom S1 is a stage and a continuant person of whom S2 is a stage are identical. (p.61) More simply: if and only if there is some one continuant person of whom both S1 and S2 are stages.’ ‘The’ implies uniqueness would preclude fission and fusion where the same stage belongs to more than one person--cases Lewis needs to deal with!

15. Fission and Fusion When mental continuity is not one-to-one

16. Fission RRRRRRRR RRRRRRRR • A stage may be R-related to stages that are not R-related to one-another • Given such branching cases, the R-relation is not transitive! RRRRRRRR

17. Identity and I-relatedness • If the R-relation is the I-relation then the I-relation can’t be transitive either • But identity is transitive • No problem: person-stages S1 and S2 are I-related iffa continuant person of whom S1 is a part is a stage of a continuant person of whom S2 is a state are identical. • No problem??? On Lewis’ account there are two people all alongin fission cases.

18. The I-relation is not transitive S3 S2 S1 • S1 is I-related to S2 because there’s a person of which both are stages and • S1 is I-related to S3 for the same reason • But there’s no person of which S2 and S3 are stages so S2 and S3 aren’t I-related to one another!

19. Synchronic Counting • Counting how many people are around at a given time • In fission cases continuant persons overlap (like some roads!) so before fission there will be two ‘continuant’ persons sharing a stage and… • From the timeless perspective, in a fission case, two people all along--who ‘cohabit’ before fission! • Lewis solution: synchronic counting is not by identity but by ‘tensed identity’, a derivative relation among continuants induced by identity among stages • Tensed Identity: C1 and C2 are identical-at-a-time-t iff they both exist at t and their stages at t are identical.

20. Different People Identical-at-t S3 S2 S1 • There are two people at all times • They are identical-at-t--and neither they nor anyone else can tell them apart at t! • The name ‘Jones’ is ambiguous t’ t Jones

21. Tensed Identity • Is this ok? Some hold (controversially) that identity is the counting relation… • Lewis: A counting relation has at least to be an equivalence relation: reflexive, symmetrical, and transitive--and tensed identity is. • Lewis: A counting relation must be an indiscernibility relation…for at least some significant class of properties • Identity-at-t is an indiscernibility relation for those properties of a person determined by his stage at t

22. Recall Smith-Jones and Brown-Jones We split Jones brain and transplant the two hemispheres (which duplicate information) into the otherwise brainless bodies of Smith and Brown. After the operation, both Smith-Jones and Brown-Jones sincerely claim to be Jones. They can’s both be identical to Jones! Smith-Jones Brown-Jones Jones

23. What, at t,will be true about Jones? S3 S2 S1 Brown-Jones cleans outthe bank accountand flies to Italy. Spends rest of life living well in Florence Retirement savingsgone, Smith-Jonesretires toChula Vista • Which is true: ‘Jones will live in Chula Vista’ or ‘Jones will live in Florence’? • Both--since ‘Jones’ is ambiguous. • But ‘Jones will live in Chula Vista and Florence’ isnot true! Jones

24. Longevity When mental connectedness fades away

25. Is survival a matter of degree? • The complex fission-fusion case considered by Parfit suggests that psychological continuity may be a matter of degree. • Lewis suggests that in the Methusalah case psychological continuity may be a matter of degree also. { { { { time

26. Methusalah(not to scale) Consider Methuselah. At the age of 100 he still remembers his childhood. But new memories crowed out the old. At the age of 150 he has hardly any memories that go back before his twentieth year. At the age of 200 he has hardly any memories that go back before his seventieth year…When he dies at the age of 969 he has hardly any memories that go beyond his 839th year. { { { { time

27. More Overlap than in Fission Cases • Any two stages of Methusalah separated by no more than 137 years are R-related • Any two stages separated by 137 years or more are not R-related. • Segments of Methuselah are R-interrelated iff no more than 137 years apart. • Since the R-relation and I-relation are the same, all and only segments exactly 137 years long are maximal I-interrelated aggregates, i.e. continuant persons. • There are infinitely many overlapping persons! • Lewis: ‘Tensed identity to the rescue once more’

28. Degree Personal identity is a matter of degree because personhood is

29. Survival a Matter of Degree • In Parfit’s case of fusion the persons involved (considered as 4-dimensional worms) have less personhood than in ordinary cases. • R-relatedness is some unspecified combination of non-transitive connectiveness and continuity so may fade away (continuity not sufficient!) • Compare to ordinary case of diminished personhood involving ‘deficient stages’. • ’If we say that a continuant person is an aggregate of R-interrelated person-stages, it is clear that personhood admits of degree’. • [Could this be a reason not to say a continuant person is an aggregate of stages?]

30. Degrees of Personhood • Delineation of boundary: stringency requirement for 2 stages being R-related is set. • Determines both which aggregates are R-related and which are maximal • The more delineations according to which two stages are I-related, the higher the degree of personhood and • The higher the degree of R-relatedness • So, wherever we set the cut-off for I-relatedness, the degree of R-relatedness will track the degree of I-relatedness

31. S1 S2 S3 S4 S5 S6 Deliniation 3 • Stages’ degree of I-Relatedness: I-related under more delineations--more I-related • Stages S2 and S3 are I-related under Delineations 1, 2, and 3; Stages S2 and S5 under Delineations 1 and 2, but not 3; Stages S1 and S6 only under Delineation 1 • Segment S2 - S3 is I-interrelated to a higher degree than S2 - S4 so has a higher degree of personhood; Segment S2 - S4 has higher degree of personhood than Segment S1 - S6 • Degree of Personhood = Degree of R-Interrelatedness Deliniation 2 Deliniation 1

32. Perry’s Treatment of Fission And then there were three…

33. And Then There Were Three Smith-Jones Brown-Jones • Persons’ names pick out lifetimes traced from stages that occur at different times. • A lifetime is the aggregate of stages we get tracing the whole path of the (intransitive!) R-relation from a given stage. Jones

34. Postscript Two Minds With But a Single Thought

35. A Case of Semi-Failed Teletransportation Martha post-fission stage m on Mars • Problem: Eartha’s pre-fission desire, in virtue of stage e’s desiring, to get to Mars is not satisfied since she, a 4-d worm, does not include a stage on Mars. • Lewis Response: ‘There is a limit to how commonsensical one’s desires can possibly be under the peculiar circumstances of stage-sharing. • Comment: maybe the problem is understanding people as 4-d worms Eartha pre-fission stage e on Earth Cohabitants Branch Line Case

36. Problem: The First-Person Perspective • Lewis: If you wonder whether you will survive the coming battle or what‐ not, you are wondering whether any of the stages that will exist afterward is R‐related to you‐now, the stage that is doing the wondering. • Thoughts are temporally perspectival: we’re concerned about our survival and consider ourselves responsible for past actions from a temporal perspective. • From my temporal perspective I look ahead and wonder whether I will survive • And, intuitively, nothing other than the relation that my current person-stage bears to future person-stages should make any difference. • Intuitively, personal survival is intrinsically grounded…

37. In Defense of Stages Lewis defends the four-dimensionalist ontology of instantaneous stages

38. Another alternative Both Lewis’ account and Perry’s assume that continuant persons are space-time worms rather than stages worm A stage is a ‘temporalslice’ of a worm stage

39. The Stage Language • On the stage account individuals are just stages. • Names are systematically ambiguous (like indexicals) • They pick out different stages at different times Jones Jones

40. Worms or Stages? • Assuming 4-dimensionalism, there is a further question: are ordinary objects, including people, 4-d ‘worms’ that have instantaneous stages as their temporal parts or are they themselves instantaneous stages? worm stages

41. In Support of the Stage Theory • Ontology is same as Worm Theory: difference just in semantics • Persons are instantaneous stages but • Persons aren’t don’t live and die at a moment: they survive by being R-related to later stages • The First Person Perspective • The Personite Problem • Time Preference: discounting the future.

42. The Stage Language Jones Smith-Jones Brown-Jones • Future tense statements about a person really say that the stage which he is, is R-related to another stage that is whatever. • [Before fission] Jones will be in room 102 after fission because the pre-fission stage ‘Jones’ picks out is R-related to a post-fission stage in room 102. Jones Jones

43. Bad, Bad, and Bad • All three accounts assume (or are compatible with) a four-dimensionalist ontology but chop it up differently, i.e. have different accounts of what persons and other ordinary objects are, and all are bad in their own way. • Ordinary objects are branches (Lewis): ’Cohabitation’ is fission cases--two or (possibly many!) more indistinguishible objects around before fission. • Ordinary objects are instantaneous stages (Sider): gets synchronic counting right counting by identity, but in diachronic counting, for ordinary as well as fission cases there are infinitely many objects. • Ordinary objects are lifetimes (Perry): cannot count timelessly at all.

44. The End