Persistence Of Objects Over Time Notes

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.”

  • 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 t₁t₀ and goes out of existence at some time t₂t₃ and takes up some portion of the space that O takes up for all the time that P exists.”

  • She thinks physical objects are three-dimensional and enduring through time.

  • 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:

  • Time seems to have a direction.

  • Our perception along the termporal dimension is only one-directional and is discontinuous.

  • 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.”

  • “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.”

  • “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.”

  • How does this link to the principle of unrestricted mereological composition?

  • “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.”

  • “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...

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