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Persistence Of Objects Over Time Notes

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Persistence 'Identity through Time' - Roderick Chisholm
? "[W]e use the locution 'A is B' or 'A is identical with B', in a loose sense, if we use it in such a way that is consistent with saying 'A has a certain property that B does not have' or 'Some things are true of A that aren't true of B'."
? "[A]ny ens successivum [e.g. a table] may be viewed as a logical construction upon the various things that may be said to do duty for it."
? "Some of the properties that the table has at any give time are...
such that the table borrows them from the thing that constitutes it at that time; but others are not." o The latter are essential properties.
? x is at t a table successor of y at t' = Df (i) t does not begin before t'' (ii) x is a table at t, and y is a table at t'; and (iii) x has at t every property P such that (a) y has P at t' and (b) all direct table successors of anything having P have P."
? x constitutes at t the same successive table that y constitutes at t'
= Df either (a) x and only x is at t a table successor of y at t', or (b) y and only y is at t' a table successor of x at t."
? x constitutes at t a successive table = Df There are a y and a t' such that y is other than x, and x constitutes at t the same table that y constitutes at t'.
? The ens successivum and the thing that constitutes it at any given time are exactly alike at that time with respect to all those properties which are such that they are not essential to either and they may not be rooted outside the times at which they are had.
? "The sense in which we may say that there is the successive table is not the sense in which we may say that there is the individual thing AB, or BC, or CD." 'Temporal Parts of Four-Dimensional Objects' - Mark Heller
? "On Thomson's account, a temporal part of O, call it P, is an object that comes into existence at some time t1[?]t0 and goes out of existence at some time t2[?]t3 and takes up some portion of the space that O takes up for all the time that P exists." o She thinks physical objects are three-dimensional and enduring through time. o But Heller thinks they are 4D.
? "The whole object must fill up all of its boundaries and, therefore, does not exist at a single moment."
? An object's temporal characteristics are not completely analogous to its spatial characteristics, because time is different to the spatial dimensions: o Time seems to have a direction. o Our perception along the termporal dimension is only onedirectional and is discontinuous. o Temporal units of measurement are not of the same kind as spatial units.

??????"[B]ecause a thing's parts are no more ontologically fundamental than the thing itself, existence of four-dimensional objects in no way depends upon their being built up out of instantaneous objects." On quantum mechanics: "If there is real indeterminacy in the world, if there really is no fact of the matter as to whether a given region of spacetime is full, then the world is really imprecise, and that must be reflected in the true ontology." o "This is a very different sort of imprecision from that which is involved in the vagueness of our everyday objects...the imprecision here arises from the structure of the world, not just from our way of conceptualizing the world." "A four-dimensional object is the material content of a filled region of space-time." o "A spatiotemporal part of such an object is the material content of a subregion of the space-time occupied by the whole." "To loosely say that [something] exists now is to strictly say that the present time is within [that thing's] temporal boundaries." This view avoids the Ship of Theseus paradox - objects can overlap if they share temporal parts. According to the 3D picture, if something exists now, then it has no parts that do not exist now. "If we accept a four-dimensional view of physical objects, then all it is for an object to come into existence at t0 is for it to have t0 as its lower temporal boundary." But this is problematic on the 3D view. "It is the causal mechanisms together with the material configuration of matter at any given time that affect which parts will exist at the next moment." Chisholm thinks that people do not have temporal parts because of their unity/continuity of consciousness. "[E]very filled region of space-time contains a physical object, and which of these objects we count as people is a matter of convention." o How does this link to the principle of unrestricted mereological composition?
o "Though the parts of a person may hold together in a special way, that special way is not privileged when it comes to existence." "It is just a matter of contingent fact that that causal connectedness does lead to a person's experiencing a unity of consciousness." o "But if we had been hard-wired differently, if the relevant causal connections had been different, then the thing composed of me-at-t1 and you-at-t2 might have had a unity of consciousness." "My response to Chisholm is that if an individual's experiencing a unity of consciousness or an individual's actually having a unity of consciousness can be explained on an ontology that does not allow

for temporal parts, then they can also be explained on an ontology that does allow for temporal parts - even an ontology that holds that what makes any particular collection of temporal parts add up to a person is mere convention." 'The Problem of Temporary Intrinsics' - David Lewis
? "Perdurance corresponds to the way a road persists through space; part of it is here and part of it is there, and no part is wholly present at two different places."
? "Endurance corresponds to the way a universal, if there are such things, would be wholly present wherever and whenever it is instantiated."
? The problem of temporary intrinsics: persisting things clearly change their intrinsic properties. This observation is inconsistent with the thesis of endurance.
? 3 possible solutions:

1. Deny that shapes are intrinsic properties (and say that this is what changes in a person over time). E.g. say shape is a disguised relation that an enduring thing bears to times.

2. Say that the only intrinsic properties of a thing are those it has at the present moment. I.e. there are no other times.

3. Deny that the different shapes, and the different temporary intrinsics generally, belong to the same thing. I.e. accept perdurance. E.g. the different temporal parts of one person have different intrinsic properties. 'Identity, Ostension, and Hypostasis' - Quine
? "[A] river stage is at the same time a water stage, but two stages of the same river are not in general stages of the same river."
? "Hume's theory was that the idea of external objects arises from an error of identification."
? "By pointing to more and more stages additional to a and b, however, we eliminate more and more alternatives, until our listener, aided by his own tendency to favor the most natural groupings, has grasped the idea."
? "In ostension, spatial spread is not wholly separable from temporal spread, for the successive ostensions which provide samples over the spatial spread are bound to consume time."
? "Without identity, n acts of ostension merely specify up to n objects, each of indeterminate spatiotemporal spread."
? "If it happens in this particular discourse that whatever is affirmed of any momentary object is affirmed also of every other which is river-kindred to it, so that no distinction between stages of the same river are relevant, then clearly we can gain simplicity by representing our subject matter as comprising a few rivers rather than the many river stages."
? Identification of indiscernibles: objects indistinguishable from one another within the terms of a given discourse should be construed as identical for that discourse.
? "An income group is just as concrete as a river or a person, and, like a person, it is a summation of person stages."


In contrast to how we ostensively explain the Cayster river, when we do so for 'square', "we point to various particulars and say each time 'This is square without imputing identity of indicated object from one occasion to the next." "Concepts are language, and the purpose of concepts and of language is efficacy in communication and in prediction. Such is the ultimate duty of language, science, and philosophy, and it is in relation to that duty that a conceptual scheme has finally to be appraised." Dimensionalism - Theodore Sider "According to the 'four-dimensional' conception of persons (and all other objects that persist over time), persons are a lot like their stories. Just as my story has a part for my childhood, so I have a part consisting just of my childhood." "My spatial parts extend through time like I do." "Reverse time and space in this description and we obtain a description of my temporal parts, which extend through space like I do but are smaller than I, temporally speaking; they are what you get by slicing me along a temporal dimension." "A person's journey through time is like a road's journey through space. The dimension along which a road travels is like time, a perpendicular axis across the road is like space. Parts cut the long way - lanes - are like spatial parts, whereas parts cut crosswise are like temporal parts." "A road changes from one place to another by having dissimilar subsections...I change from sitting to standing by having a temporal part that sits and a later temporal part that stands." I.e. objects perdure. Leibniz's law: x = y only if x and y have all the same properties. o But this seems to prohibit anything's surviving any change. Also problem of how two distinct things can coincide spatially (e.g. lump of clay and statue). o Solved if you accept the existence of temporal parts. Also ship of Theseus problem case. "Acceptance of four-dimensionalism is plausibly accompanied by acceptance of another metaphysical principle, the principle of unrestricted mereological composition according to which, for any objects, there exists such a thing as the mereological sum, or fusion ofthose objects - a larger object that contains [exactly]
those objects as parts." o Not necessary for four-dimensionalism, but natural. "Worms formed from person stages that are not psychologically united, for example that consist of my stages until age 3 and Bill Clinton's stages thereafter, do not fall under the predicate 'person', nor any other everyday predicate, and so are usually ignored." (Even though they exist). "Perhaps our concept of a ship does not emphasize sameness of planks, and applies to spacetime worms that continue in ship form even if they exchange planks."

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