Philosophy Of Personal Identity

[Nihil Obstat]

Does anyone here know enough about the philosophy behind personal identity to have a conversation with me about it? I find the whole concept very perplexing as one examines it more closely.

The question is "how does a person persist from time 1 (t[sub]1[/sub]) to time 2 (t[sub]2[/sub])?

Basically we have three theories:

Soul theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if their soul persists from t[sub]1[/sub] to t[sub]2[/sub],

Body theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if their body (as a living thing with the capacities thereof persists from t[sub]1[/sub] to t[sub]2[/sub],

Psychological connectedness (memory) theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if they maintain memory or mediate memory at t[sub]2[/sub] of t[sub]1[/sub].


Specifically, we can also ask (philosophically, of course) whether immortality is logically possible after bodily death, as we look deeper into Soul Theory and PC Theory.



So, anyone want to start, or am I going to be pondering this on my own for a while?

Edited December 3, 2009 by Nihil Obstat

[Gregorius]

you will be pondering it on your own for a while.

[Nihil Obstat]

[quote name='Gregorius' date='02 December 2009 - 10:20 PM' timestamp='1259814040' post='2013596']
you will be pondering it on your own for a while.








[/quote]
We shall see. It'll be well worth the effort if someone can help me get any further along.

[Veridicus]

[quote name='Nihil Obstat' date='02 December 2009 - 11:15 PM' timestamp='1259813749' post='2013592']
Does anyone here know enough about the philosophy behind personal identity to have a conversation with me about it? I find the whole concept very perplexing as one examines it more closely.

The question is "how does a person persist from time 1 (t[sub]1[/sub]) to time 2 (t[sub]2[/sub])?

Basically we have three theories:

Soul theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if their soul persists from t[sub]1[/sub] to t[sub]2[/sub],

Body theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if their body (as a living thing with the capacities thereof persists from t[sub]1[/sub] to t[sub]2[/sub],

Psychological connectedness (memory) theory: A person persists from t[sub]1[/sub] to t[sub]2[/sub] if they maintain memory or mediate memory at t[sub]2[/sub] of t[sub]1[/sub].


Specifically, we can also ask (philosophically, of course) whether immortality is logically possible after bodily death, as we look deeper into Soul Theory and PC Theory.



So, anyone want to start, or am I going to be pondering this on my own for a while?
[/quote]

I wish I had the free time to get deep into all of this stuff. Jealous. As an aside (and before I bow out from discussion), I do not think the 3 theories are necessarily juxtaposed in isolation from eachother.

[Nihil Obstat]

[quote name='Veridicus' date='02 December 2009 - 10:41 PM' timestamp='1259815288' post='2013606']
I wish I had the free time to get deep into all of this stuff. Jealous. As an aside (and before I bow out from discussion), I do not think the 3 theories are necessarily juxtaposed in isolation from eachother.
[/quote]
I'm sure they need not be. Talking about one invariably leads you to talk about another. One of the basic papers my class was using is John Perry's Dialog on Personal Identity and Immortality.

[Laudate_Dominum]

[quote name='Nihil Obstat' date='02 December 2009 - 11:15 PM' timestamp='1259813749' post='2013592']
Does anyone here know enough about the philosophy behind personal identity to have a conversation with me about it? I find the whole concept very perplexing as one examines it more closely.

The question is "how does a person persist from time 1 (t[sub]1[/sub]) to time 2 (t[sub]2[/sub])?
[/quote]
Haven't really thought about it in recent years, but it would seem that my own view on the matter is influenced by realist phenomenology. I suppose for starters I would ask how it is that anything persists from time 1 to time 2? How you answer that question, and how you understand the concept of 'person' will surely come into play in any attempt at answering your question. Indeed, I would say that the way in which many philosophers approach the problem of personal identity says a lot about their ontology and philosophical anthropology.

[Nihil Obstat]

[quote name='Laudate_Dominum' date='02 December 2009 - 10:46 PM' timestamp='1259815613' post='2013612']
Haven't really thought about it in recent years, but it would seem that my own view on the matter is influenced by realist phenomenology. I suppose for starters I would ask how it is that anything persists from time 1 to time 2? How you answer that question, and how you understand the concept of 'person' will surely come into play in any attempt at answering your question. Indeed, I would say that the way in which many philosophers approach the problem of personal identity says a lot about their ontology and philosophical anthropology.
[/quote]
I hear that the branch of determining how objects persist (mereology) is among the most complicated of all the philosophical branches. Let's change the question then, from "how does a person exist..." to "how do you exist..." so that we don't have to approach personhood. We could even address it personally "I persist because...".

Realist phenomenology code for "common sense"?

[Laudate_Dominum]

[quote name='Nihil Obstat' date='02 December 2009 - 11:52 PM' timestamp='1259815963' post='2013617']
I hear that the branch of determining how objects persist (mereology) is among the most complicated of all the philosophical branches. Let's change the question then, from "how does a person exist..." to "how do you exist..." so that we don't have to approach personhood. We could even address it personally "I persist because...".

Realist phenomenology code for "common sense"?
[/quote]

[Laudate_Dominum]

[quote name='Nihil Obstat' date='02 December 2009 - 11:52 PM' timestamp='1259815963' post='2013617']
I hear that the branch of determining how objects persist (mereology) is among the most complicated of all the philosophical branches.[/quote]
I don't know if that is true, but I do know that you can get a zillion different answers to what are the most complicated of all philosophical branches. The last time I thought about myself I concluded that ethics was the thorniest branch of philosophy, but who can really say? haha

[quote name='Nihil Obstat' date='02 December 2009 - 11:52 PM' timestamp='1259815963' post='2013617']
Let's change the question then, from "how does a person exist..." to "how do you exist..." so that we don't have to approach personhood.[/quote]
I don't believe it would be proper to discard the question of personhood when trying to describe personal identity. Perhaps we could deny personhood and view personal identity as something indistinct from plain individuality.

[quote name='Nihil Obstat' date='02 December 2009 - 11:52 PM' timestamp='1259815963' post='2013617']
We could even address it personally "I persist because..."[/quote]
Nah, reminds me of psychology class too much. haha.

[Laudate_Dominum]

[quote name='Nihil Obstat' date='02 December 2009 - 11:52 PM' timestamp='1259815963' post='2013617']
Realist phenomenology code for "common sense"?
[/quote]
I'm not sure about your meaning here, nor do I quite understand what the tongue smilies are meant to signify.

I didn't put forth my position in that post, I am only curious to know how you are approaching the topic. Are you wearing the hat of an empiricist, a thomist, a transcendental feuerbachian space hippie? I did mean to indicate that I've been able to make some sense of the issues in the past thanks to realist phenomenology.

[Nihil Obstat]

[quote name='Laudate_Dominum' date='02 December 2009 - 11:03 PM' timestamp='1259816609' post='2013623']
I don't know if that is true, but I do know that you can get a zillion different answers to what are the most complicated of all philosophical branches. The last time I thought about myself I concluded that ethics was the thorniest branch of philosophy, but who can really say? haha


I don't believe it would be proper to discard the question of personhood when trying to describe personal identity. Perhaps we could deny personhood and view personal identity as something indistinct from plain individuality.


Nah, reminds me of psychology class too much. haha.
[/quote]
Here's some mereology for you: ( )

4.4. Unrestricted Composition

The strongest versions of all these composition principles are obtained by asserting them as axiom schemas holding for every condition ψ, i.e., effectively, by foregoing any reference to ψ altogether. Formally this amounts in each case to dropping the second conjunct of the antecedent, i.e., to asserting the schema expressed by the relevant consequent with the only proviso that there are some φ-ers. For example, the following schema is the unrestricted version of (P.15ψ), to the effect that every specifiable non-empty set of entities has a sum:

(P.15) Unrestricted Sum
∃wφw → ∃z∀w(Ozw ↔ ∃v(φv ∧ Ovw))
The extension of EM obtained by adding every instance of this schema has a distinguished pedigree and is known in the literature as General Extensional Mereology, or GEM. It corresponds to the classical systems of Leśniewski and of Leonard and Goodman, modulo the underlying logic and choice of primitives. Similar theories can be obtained by extending EM with the unrestricted versions of (P.15ψ,a) and (P.15ψ,b). Two indicative examples may be found in Landman (1991) and Lewis (1991), respectively (though the latter relies on the machinery of plural quantification rather than schematic formulas), whereas a weaker theory endorsing only the unrestricted version of (P.14ψ) may be found in Whitehead (1919).

GEM is a powerful theory, and it was meant to be so by its nominalistic forerunners, who were thinking of mereology as a good alternative to set theory. How powerful is it? To answer this question, consider the following generalized sum operator:

(45) General Sum
σxφx =df ιz∀w(Ozw ↔ ∃v(φv ∧ Ovw))
Then (P.15) and (P.5) can be simplified to a single axiom schema:

(P.17) Unique Unrestricted Sum
∃xφx → ∃z(z=σxφx)
and we can introduce the following definitions:

(46) Sum
x + y =df σz(Pzx ∨ Pzy)
(47) Product
x × y =df σz(Pzx ∧ Pzy)
(48) Difference
x − y =df σz(Pzx ∧ Dzy)
(49) Complement
~x =df σzDzx
(50) Universe
U =df σzPzz
Note that (46) and (47) yield the binary operators defined in (35) and (42) as special cases. Moreover, in GEM the generalized Product principle (P.16ψ) is also derivable as a theorem, with ‘ψ’ as weak as the requirement of mutual overlap, and we can introduce a corresponding functor as follows:

(51) General Product
πxφx =df σz∀x(φx → Pzx).
The full strength of the theory can then be appreciated by considering that its models are closed under each of these functors, modulo the satisfiability of the relevant conditions. To be explicit: the condition ‘DzU’ is unsatisfiable, so U cannot have a complement. Likewise products are defined only for overlappers and differences only for pairs that leave a remainder. In all other cases, however, (46)-(51) yield perfectly well-behaved functors. Since such functors are the natural mereological analogues of the familiar set-theoretic operators, with ‘σ’ in place of set abstraction, it follows that the parthood relation axiomatized by GEM has essentially the same properties as the inclusion relation in standard set theory. More precisely, it is isomorphic to the inclusion relation restricted to the set of all non-empty subsets of a given set, which is to say a complete Boolean algebra with the zero element removed—a result that can be traced back to Tarski (1935: n. 4). (Actually, Tarski's result refers to a stronger version of GEM in which infinitary sums are characterized using explicit quantification over sets, rather than schematic formulas. This is of course a relevant difference, in view of Cantor's 1891 theorem. For set-free formulations which, like those considered here, strictly adhere to a standard first-order language with a denumerable supply of open formulas, the correct way of summarizing the algebraic strength of GEM is this: Any model of this theory is isomorphic to a Boolean subalgebra of a complete Boolean algebra with the zero element removed—a subalgebra that is not necessarily complete if Zermelo-Frankel set theory with the axiom of choice is consistent. See Pontow and Schubert 2006, Theorem 34, for details and proof.)

Would we get a full Boolean algebra by supplementing GEM with the Bottom axiom (P.10), i.e., by positing the mereological equivalent of the empty set? One immediate way to answer this question is in the affirmative, but only in a trivial sense: we have already seen that (P.10) along with the Supplementation axiom (P.4) admits only of degenerate one-element models. Such is the might of the null item. On the other hand, suppose we introduce the following “non-trivial” counterparts for the parthood, overlap, and disjointness predicates:

(52) Non-trivial Parthood
Poxy =df Pxy ∧ ¬∀zPxz
(53) Non-trivial Overlap
Ooxy =df ∃z(Pozx ∧ Pozy)
(54) Non-trivial Disjointness
Doxy =df ¬Ooxy
and suppose we introduce a corresponding family of “non-trivial” operators for sum, product, etc. Then it can be shown that the theory obtained from GEM by adding (P.10) and replacing the (P.5) and (P.15) with the following “non-trivial” variants:

(P.5o) ¬Pyx → ∃z(Pozy ∧ ¬Oozx).
(P.15o) ∃wφw → ∃z∀w(Oozw ↔ ∃v(φv ∧ Oovw))
is indeed a full Boolean algebra under the new operators. (See again Pontow and Schubert 2006.) This shows that, mathematically, mereology does indeed have all the resourses to stand as a robust and yet nominalistically acceptable alternative to set theory, the real source of difference being the attitude towards the nature of singletons (as already emphasized by Leśniewski 1916 and eventually clarified by Lewis 1991). As already mentioned, however, from a philosophical perspective the Bottom axiom is by no means a favorite option. The null item would have to exist “nowhere and nowhen”, said Geach (1949: 522), or perhaps “everywhere and everywhen”, and that is hard to swallow. One may try to justify the gulp in varous ways, perhaps even by construing the null item as the utimate incarnation of divine simplicity, as in Hudson (2006b: §6). But few minded philosophers would be willing to go ahead and swallow for the sole purpose of neatening up the algebra.

There are other equivalent formulations of GEM that are noteworthy. For instance, it is a theorem of every extensional mereology that parthood amounts to inclusion of overlappers:

(55) Pxy ↔ ∀z(Ozx → Ozy).
This means that in an extensional mereology ‘O’ could be used as a primitive and ‘P’ defined accordingly, as in Goodman (1951), and it can be checked that the theory defined by postulating (55) together with the Unrestricted Sum principle (P.15) and the Antisymmetry axiom (P.3) is equivalent to GEM (Eberle 1967). Another elegant axiomatization of GEM, due to an earlier work of Tarski (1929), is obtained by taking just the Transitivity axiom (P.2) together with the Sumb-analogue of the Unique Unrestricted Sum axiom (P.17). By contrast, it bears emphasis that the result of adding (P.15) to MM is not equivalent to GEM, contrary to the “standard” characterization given by Simons (1987: 37) and inherited by much literature that followed, including Casati and Varzi (1999) and an earlier version of this entry. This follows immediately from Pontow's (2004) counterexample mentioned at the end of Section 4.3, since the non-extensional model in Figure 3 satisfies (P.15), and was first noted in Pietruszczak (2000, n. 12). More generally, in Section 4.2 we have mentioned that in the presence of the ξ-Product postulate (P.13ξ), with ξ construed as overlap, the Strong Supplementation axiom (P.5) follows from the weaker Supplementation axiom (P.4). However, the model shows that the postulate is not implied by (P.15) any more than it is implied by its restricted variants (P.15ψ). Apart from its relevance to the proper characterization of GEM, this result is worth stressing also philosophically, for it means that (P.15) is by itself too weak to generate a sum out of any specifiable set of objects. In other words, fully unrestricted composition calls for extensionality, on pain of giving up both supplementation principles. The anti-extensionalist should therefore keep that in mind. (On the other hand, a friend of extensionality may welcome such a result as an argument in favor of adopting, not (P.15), but its Sumb-variant, i.e., the unrestricted version of (P.15ψ,b), for in MM that way of sanctioning unrestricted composition turns out to be enough to entail strong supplementation along with the existence of all products and, with them, of all sums. On this and related matters, indicating that the axiomatic path to “classical extensional mereology” is less clear than hitherto supposed, see Hovda 2009.)

Finally, it is worth recalling that the assumption of atomism generally allows for significant simplifications in the axiomatics of mereology. For instance, we have already seen that AEM can be simplified by subsuming (P.5) and (P.8) under a single atomistic supplementation principle, (P.5′). Likewise, it turns out that AGEM could be simplified by replacing the Unrestricted Sum postulate (P.15) with the more perspicuous

(P.15′) ∃wφw → ∃z∀w(Aw → (Pwz ↔ ∃v(φv ∧ Pwv)))
which asserts, for any non-empty set of entities, the existence of a sum composed exactly of all the atoms that compose those entities (Eberle 1967).


I don't know what it means, but it's probably very intelligent.

[Laudate_Dominum]

[quote name='Nihil Obstat' date='03 December 2009 - 12:10 AM' timestamp='1259817031' post='2013627']
Here's some mereology for you: ( )

...
[/quote]
Plenty of branches of philosophy have various systems of axiomatic formulation and formal notation. Like boolean algebra, modal logic, or javascript, once you get used to the rules and notation it isn't all that mystifying. Still, does this have something to do with your exploration of personal identity? Enlighten me cuz I haven't read the book you referred to so don't really know where ur coming from.

This thread is making me feel lost, confused, alone... sad... scared... Help?

[Nihil Obstat]

Mereology is apparently the study of identity of objects over time, rather than people. I don't know exactly why they needed to develop a whole quasi-mathematical system around it, but apparently it's necessary.

I don't know anything about it either; just looks interesting. This is only a nice little aside while I wait for anyone who is so inclined to address personal identity over time.

[Laudate_Dominum]

[quote name='Nihil Obstat' date='03 December 2009 - 12:36 AM' timestamp='1259818587' post='2013640']
Mereology is apparently the study of identity of objects over time, rather than people. I don't know exactly why they needed to develop a whole quasi-mathematical system around it, but apparently it's necessary.

I don't know anything about it either; just looks interesting. This is only a nice little aside while I wait for anyone who is so inclined to address personal identity over time.
[/quote]
I'm willing to discuss personal identity over time. Since you started the topic I'm hoping that you'll elucidate your thoughts in some detail.

[Nihil Obstat]

[quote name='Laudate_Dominum' date='02 December 2009 - 11:38 PM' timestamp='1259818720' post='2013644']
I'm willing to discuss personal identity over time. Since you started the topic I'm hoping that you'll elucidate your thoughts in some detail.
[/quote]
Ok. I can't go into great detail right now because of time constraints, but basically I'm at an impasse.

Soul theory appears to be incomplete because it can't explain why we are able to continuously re-identify other human beings over time. We don't have direct access to souls, so how exactly can we be using the soul as the identifying characteristic? (That's not to argue that there isn't a soul, just that it doesn't help in determining personal identity.)

Body theory in my opinion falls short because we can easily imagine having a body transplant, and still fundamentally being ourselves. Or, there's an invented hypothetical case in Perry's dialogue: one woman is hit by a streetcar and another has a stroke. Doctors see that they have one healthy mind and one healthy body, so they combine the two... so which survived? Most people are inclined to say that the woman whose mind was used, was the woman who survived. So intuitively body theory seems irrational.

Psychological connectedness seems more plausible at first, but it all goes to hell in a handbasket when we look at fission/fusion cases, as, I suppose, most theories will. Think about Star Trek transporters. Let's say you've got a transporter, and it functions by first making a 'readout' of your entire makeup, then destroying your elements, and sending that readout to wherever you want to go and reforming the elements there. Makes sense, right? We can imagine that this is still "you", because it is connected to you by memory stages. Well let's say that there was a problem with the machine this time. You're transported, but your elements aren't destroyed at location one. Now we have two "you's", both connected by psychological stages, but different beings. Either we have one being experiencing two incompatible experiences, which seems logically impossible, or the one being is now two entirely separate beings, and thus you did not actually "survive".