Are essential properties necessary for identity over time?: Philosophy Forums

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Are essential properties necessary for identity over time?

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Are essential properties necessary for identity over time?

treysuttle
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Posted 05/30/09 - 05:46 AM: Subject: Are essential properties necessary for identity over time?	#1
Either material objects maintain some identity over time or they do not. If some objects do maintain identity over time, then this identity (the fact that say, this apple is the same apple on my desk that was on my desk yesterday) is in virtue of its properties. But this cannot be in virtue of all (or the sum) of its properties, because of course some of its properties have altered. Therefore, there are some properties that are essential for this apple to be the same apple that it was yesterday and other properties that are not essential for it to be the same apple. (note, my issue is not to debate whether objects do in fact persist, but if the thesis that they do persist require a distinction between essential and non-essential properties).

wuliheron
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Posted 05/30/09 - 08:14 AM:	#2
You need to examine relationships as well as properties, because properties are defined by their relationships. For example, as far as anyone can tell one electron is exactly the same as any other electron. They have precisely the same properties such as charge, spin, etc. It is only through their relationships to other particles that we manage to distinguish between any two or more electrons.

treysuttle
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Posted 05/30/09 - 09:03 AM:	#3
I see what you are saying, but I am not sure where you are going with it. Consider a bright red apple. Then, several days later, the apple is brown. Of course the constituents that compose the apple have changed....electrons have changed position, particles have popped in and out of existence....whatever physics tells us goes on 'at that level'. Now, if the claim, 'The apple that was bright red several days ago is brown today' is true, then (on my constraint that I am wondering about a presupposition of the thesis in question), then in virtue of what is the apple the same apple (if its color has changed...as well as many of its fundamental constituents...electrons and so forth)? My argument is, unless we are to reject identity over time, then its being the same apple is in virtue of something -- and this seems to naturally lead to a distinction between essential properties (properties without which an object would not be the particular object that it is) and non-essential properties (properties that may change, come and go, and the object remain the particular object that it is). Of course, I don't have a theory concerning what the essential and non-essential properties of something even as basic as an apple are....its non-essential properties (color for example) seem fairly clear. My concern is whether we can maintain that objects really do persist (as an identity relation) over time and maintain that there are no properties that an object has that are essential to its being the particular object that it is.

wuliheron
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Posted 05/30/09 - 10:12 AM:	#4
The passage of time is relative to the observer, with the speed of light being the only exception to this relationship. If I am moving close to the speed of light relative to the apple its identity will not change from my perspective. Thus it can be demonstrated that my relationship to the apple is more fundamental than any concept I might have of the apple as an independent object. Taking this to the extreme, as I accelerate towards the apple and approach the speed of light the apple and, indeed, the entire universe will appear to shrink to a single blue-shifted point in front of me. As I accelerate away from the apple, it and the universe will both appear to expand and red-shift. In other words, the properties of the apple appear to change along with our relative motions. Edited by wuliheron on 05/30/09 - 10:19 AM

treysuttle
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Posted 05/30/09 - 06:34 PM:	#5
Sorry, I just don't see how that relates to my issue. Blue shift...red shift...what are the conditions that this is the same apple today that was here yesterday?

wuliheron
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Posted 05/30/09 - 07:13 PM:	#6
Today and yesterday are relative. In other words, change and the lack of change are relative to the observer. This means that even the ability to identify something as an apple is relative to the observer. If I am moving at close to the speed of light towards an apple it and the entire universe ahead of me will look like a tiny unidentifiable and unchanging pin prick of light. If I threw an apple into a black hole it would eventually appear to slow to a stop and never change. The apple would never rot, would never change color, and would never appear to move again. From my point of view, it would remain unchanging forever. However, if went in with the apple it would appear to change normally. And, again, if I moved quickly towards or away from the apple it could become completely unrecognizable as an apple. Hence, the identity of what we call an apple depends upon our relative relationship with the object more than any demonstrable "appleness" of the object. If I were in a spaceship moving towards the apple at high speed, it would go off like an atom bomb if I hit it. Totally unapple like behavior.

treysuttle
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Posted 05/31/09 - 07:46 AM:	#7
I don't deny what you are saying, i.e. under different conditions the apple will change differently and under various conditions we will perceive the change of the apple differently. Nor am I denying that what causes the change in the apple is 'relative' to conditions perhaps external to the apple (perhaps the whole universe?). What I am wondering about is, if the apple changes and yet in some sense remains the same apple, what does this imply about about the nature of the properties of the apple...

Jehu
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Posted 05/31/09 - 05:06 PM:	#8
One of Leibniz’s Laws, the “Indiscernibility of Identicals”, states that if what appears to be two or more objects are in fact identical (one and the same), there can be no property held by one and not by the other. Consequently, the two apples are not identical, though they are causally related – for there is a logical progression to the changes whereby the earlier apple undergoes a transformation into the later apple. To state the case more simply, spatio-temporal coordinates are an essential property of a object, and so nothing can be said to be identical from one moment to the next; a point which is in full accord with the fact that everything exists is a state of perpetual flux.
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YadaYada
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Posted 05/31/09 - 06:20 PM:	#9
Jehu wrote: One of Leibniz’s Laws, the “Indiscernibility of Identicals”, states that if what appears to be two or more objects are in fact identical (one and the same), there can be no property held by one and not by the other. Therefore, any two electrons are at least equivalent, and possibly identical. Consequently, the two apples are not identical, though they are causally related – for there is a logical progression to the changes whereby the earlier apple undergoes a transformation into the later apple. Yes. But this causality is contingent, not necessary. It is easier to say historically that the rotten apple was the "same but not identical" (?!) apple than to say that the apple will be rotten tomorrow. To state the case more simply, spatio-temporal coordinates are an essential property of a object, and so nothing can be said to be identical from one moment to the next; a point which is in full accord with the fact that everything exists is a state of perpetual flux. I'm with you. But flux is not a constant but is different from object to object, and from one type of object to another type. The Parmenidean world is therefore not absolutly static, but just a slower changing world viewed from a faster changing point of observation. And the Heracleitan is the other way around -- the river flows past a relatively stable observer.
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Cuthbert
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Posted 05/31/09 - 11:41 PM:	#10
Perhaps there are no essential properties but there is still identity over time. The apple remains the same just in case enough of its properties remain the same for it to be the same apple. 'Enough' is vague and the vagueness is a universal feature of our concepts of material objects. Or, the apple is the same apple if apple(t) is causally-historically linked to apple(t+1) in particular ways. 'Particular' ways is vague, varying between kinds of material objects, and again the vagueness is a universal feature of our concepts. We have a rough idea of what it is for any given kind of material object to be the same over time. If we lived a life in which a rough idea was not adequate then we would need a new language. Until then, we're fine. (It could be said that life at the quantum level would be such a life. And we do need a new language at that level, because our everyday one lets us down in paradox and contradiciton.)

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