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## Re: [ontolog-forum] Incompatibilities in 3D to 4D

 To: "'[ontolog-forum] '" Matthew West Tue, 10 Mar 2009 17:37:38 -0000 <49b6a571.0707d00a.4d04.22b7@xxxxxxxxxxxxx>
 Dear Ali,     Hi all,   For those who are interested, check out: Mark Hinchliff (1996), The Puzzle of Change. Philosophical Perspectives, 10, Metaphysics, 1996. pp. 119-136.  for a nice overview of the issues at hand here.   ·         [MW] I also recommend: Hawley, Katherine How things persist Oxford: Clarendon Press 2001 ·           In  Trenton Merricks (1999) Persistence, Parts and Presentism, NOUS 33:3 (1999) 421-438 we get two nice definitions of the two accounts:   (1) For any presently existing object 0, 0 endures if and only if 0 persists and all of O's parts simpliciter exist at the present time. I I   We can give a parallel account of what it is for an object to perdure: (2) For any presently existing object 0, 0 perdures if and only if 0 persists and some of O's parts simpliciter do not exist at the present time.   While in Storrs McCall & EJ Lowe (2003). “3D/4D Equivalence, the Twins Paradox, and Absolute Time,” Analysis 63, pp. 114–23. and McCall & Lowe (2006). "The 3D/4D Controversy: A Storm in a Teacup." NOUS 40:3 (2006) 570–578 we get an argument for the equivalence of the two perspectives.  They come closest to actually positing axioms showing equivalence:   The reader will have noticed that there is a close similarity between the set of 3D particles which constitute an enduring object O at a time t, and the instantaneous 4D temporal part of O at t. This fact provides for a simple translation scheme between the 4D temporal parts ontology and the 3D particle ontology. Let T(O, t) be the instantaneous 4D temporal part of O at t, and let be the instantaneous 3D sum of the particles which constitute O at t. In 4D ontology, O is the mereological fusion of all its temporal parts T(O, t), one for each moment at which O exists. In 3D ontology, O is the set of particles which successively constitute it at each moment O exists, a set which “changes”, i.e. is replaced by a new set, each time O gains a new particle or loses an old one. To translate from the 4D to the 3D description of O, reduce O to its temporal parts, and replace each temporal part T(O, t) by the momentary sum of particles which constitute O at t. The collection of all such momentary sums , for every time at which O exists, yields the set of sets of 3D particles which successively constitute O. Conversely, to translate from the 3D to the 4D description of O, first reduce O to the momentary sums of particles which constitute it, then replace each by the corresponding temporal part T(O, t), then reconstruct O as the fusion of its temporal parts.   I haven't been successful at finding people who disagree with McCall and Lowe's observations, the closest is in a phd thesis found here:   [MW] You need to remember that this is written from a 3D perspective. Strictly, 4D can say things that 3D cannot (no concern to a 3Dist since they would not want to say them). So strictly this is a full mapping in one direction and a partial mapping in the other. The other thing I notice here is that the equivalence seems to be presented in terms of stage theory for 4D rather than perdurance theory (Hawley’s terminology). The stage theory version of 4D has an infinite number of temporal slices linked by some sort of “followed by” relation. Perdurance theory allows for objects that a truly extended in time as well as space. The account above does not seem to account for temporal parts that are not temporal stages, but aggregates of them.   Gibson (2007) Time, Objects, and Identity - pihlisci archive, Oxford PhD (section 6.4).    He argues, (rightly imo) that their appeal to particles is unnecessary and potentially distracting. He also seems to assert that their position is of ontological equivalence, tho McCall and Lowe never explicitly state this. These two points aside, Gibson's major quibble arises from the equivalence between 4D-3D being based (implicitly) on linking X with "the life of X." Based on this, Gibson notes that the parts of one's life are not equivalent to X himself.   [MW] Do you mean here “the sum of the parts of one’s life” or “each part of one’s life”? The sum is equivalent to the person, but each part is not (try counting how many people you get if this were true).   I don't agree with this line of reasoning as it seems to me he is conflating several senses of life to derive this apparent oddity, the sense of life required for the mapping to work is exactly that which captures X and his properties as the parts of X's life. Whether this is too technical a definition to be palatable is another issue, which imo, doesn't affect engineering / business considerations. If it is so objectionable, let's call it not "life of X", but "X through his life."   [MW] Well both of these are implicitly 3D views. A 4Dist would simply say X and temporal parts of X.   Anyhow, I thought I'd post this to the forum and see what people have to say.   For the record, I don't believe that the 3D-4D translation provided in McCall and Lowe (2006) is ontological equivalence. [MW] What is ontological equivalence? Moreover, for someone developing ontologies for practical applications, i think logical equivalence suffices.  Anyone disagree? [MW] What is logical equivalence?     Finally, as many have pointed it, we haven't really come across any ontology which has formalized these notions of perdurance and endurance. I would imagine if one wanted to actually enforce a 4D view in an ontology, they'd need a second order axiom, otherwise, they could use CL's ability to quantify over explicit relations via an axiom similar too   [MW] It would not be valid to talk about X at different times. You would have to talk about objects that were temporal parts of X. You would need to enforce it through identity criteria (I  think). Each particular object has exactly one temporal extent during which it exists (though this does not need to be contiguous). No two objects have the same spatio-temporal extent (not all 4Dists insist on this).   whenever you have a relation (i.e. Rel1)  you want to be restricted to the 4d view, you would state:   (forall (Rel1)  (4DRel Rel1))   then you would have to have something akin to:   (forall (R ...)     (if   (4Drel R)           (exists (t)              (and (R ... t) (time t) (argument ...) ) )))   [MW] I don’t really follow that I’m afraid. Can you give a clue as to what the variables/constants mean, and which is which.   with appropriate axioms to define what an argument is. Though this style is coming perilously close to mixing meta concepts with the ontology itself.   Yet without a set of axioms, whether at the metaontology level or within the ontology, it is nigh impossible to develop a mapping through which one could prove, at least, logical equivalence between the two view points.   [MW] I agree. Happy to work with you on what the 4D axioms might be. Pat H probably knows what they are anyway.   As Michael Gruninger pointed out though, there is high similarity between the notions of 3D-4D and time intervals and time points. While the latter are clearly not ontologically equivalent, their extensions may be mapped to logical equivalence over particular domains.   [MW] Not quite sure what you are saying here, but a 4D notion of time is rather different to the 3D ones I am used to. For 4D a point in time is a projection across all space at a time, rather than a point on a time line.     Regards   Matthew West                            Information  Junction Tel: +44 560 302 3685 Mobile: +44 750 3385279 matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx http://www.matthew-west.org.uk/   This email originates from Information Junction Ltd. Registered in England and Wales No. 6632177. Registered office: 2 Brookside, Meadow Way, Letchworth Garden City, Hertfordshire, SG6 3JE.     Cheers,   Ali -- (•`'·.¸(`'·.¸(•)¸.·'´)¸.·'´•) .,.,
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 Current Thread Re: [ontolog-forum] Incompatibilities in 3D to 4D, (continued) Re: [ontolog-forum] Incompatibilities in 3D to 4D, Ali Hashemi Re: [ontolog-forum] Incompatibilities in 3D to 4D, Matthew West Re: [ontolog-forum] Incompatibilities in 3D to 4D, Ali Hashemi Re: [ontolog-forum] Incompatibilities in 3D to 4D, Matthew West Re: [ontolog-forum] Incompatibilities in 3D to 4D, Ali Hashemi Re: [ontolog-forum] Incompatibilities in 3D to 4D, John F. Sowa Re: [ontolog-forum] Incompatibilities in 3D to 4D, Christopher Menzel Re: [ontolog-forum] Incompatibilities in 3D to 4D, Pat Hayes Re: [ontolog-forum] Incompatibilities in 3D to 4D, Michael Gruninger Re: [ontolog-forum] Incompatibilities in 3D to 4D, John F. Sowa Re: [ontolog-forum] Incompatibilities in 3D to 4D, Matthew West <=