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9. Objects / C. Structure of Objects / 8. Parts of Objects / b. Sums of parts

[the concept of parts treated as one concept]

22 ideas
A 'whole' (rather than a mere 'sum') requires an internal order which distinguishes it [Aristotle]
     Full Idea: In the case of a quantity that has a beginning, a middle and an end, there are those instances in which the order does not create a differentia, which are said to be 'sums', and those is which it does, which are said to be 'wholes'.
     From: Aristotle (Metaphysics [c.324 BCE], 1024a01-5)
     A reaction: This is the reason why Aristotle is so much better than the run-of-the-mill naïve modern metaphysician.
If a syllable is more than its elements, is the extra bit also an element? [Aristotle]
     Full Idea: The syllable is something - not only its elements (the vowel and the consonant) but also something else; ...that something must itself be either an element or composed of elements.
     From: Aristotle (Metaphysics [c.324 BCE], 1041b16-19)
     A reaction: This pinpoints the key initial question, not just about the claims of 'holism', but about the whole puzzle of what give objects their identity?
A body is always the same, whether the parts are together or dispersed [Hobbes]
     Full Idea: A body is always the same, whether the parts of it be put together or dispersed; or whether it be congealed or dissolved.
     From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07)
     A reaction: This appears to be a commitment by Hobbes to what we now call 'classical' mereology - that any bunch of things can count as a whole, whether they are together or dispersed. He seems to mean more than a watch surviving dismantling.
The place of a thing is the sum of the places of its parts [Newton]
     Full Idea: The place of a whole is the same as the sum of the places of the parts, and is therefore internal and in the whole body.
     From: Isaac Newton (Principia Mathematica [1687], Def 8 Schol)
     A reaction: Note that Newton is talking of the sums of places, and deriving them from the parts. This is the mereology of space.
If x is ever part of y, then y is necessarily such that x is part of y at any time that y exists [Chisholm, by Simons]
     Full Idea: Chisholm has an axiom: if x is a proper part of y, then necessarily if y exists then x is part of it. If x is ever part of y, they y is necessarily such that x is part of y at any time that y exists.
     From: report of Roderick Chisholm (Person and Object [1976], p.149) by Peter Simons - Parts 5.3
     A reaction: This is Chisholm's notorious mereological essentialism, that all parts are necessary, and change of part means change of thing. However, it looks to me more like a proposal about what properties are necessary, not what are essential.
In mereology no two things consist of the same atoms [Lewis]
     Full Idea: It is a principle of mereology that no two things consist of exactly the same atoms.
     From: David Lewis (Parts of Classes [1991], 2.3)
     A reaction: The problem with this is screamingly obvious - that the same atoms might differ in structure. Lewis did refer to this problem, but seems to try to wriggle out of it, in Idea 15444.
Trout-turkeys exist, despite lacking cohesion, natural joints and united causal power [Lewis]
     Full Idea: A trout-turkey is inhomogeneous, disconnected, not in contrast with its surroundings. It is not cohesive, not causally integrated, not a causal unit in its impact on the rest of the world. It is not carved at the joints. That doesn't affect its existence.
     From: David Lewis (Parts of Classes [1991], 3.5)
     A reaction: A nice pre-emptive strike against all the reasons why anyone might think more is needed for unity than a mereological fusion.
Given cats, a fusion of cats adds nothing further to reality [Lewis]
     Full Idea: Given a prior commitment to cats, a commitment to cat-fusions is not a further commitment. The fusion is nothing over and above the cats that compose it. It just is them. They just are it. Together or separately, the cats are the same portion of Reality.
     From: David Lewis (Parts of Classes [1991], 3.6)
     A reaction: The two extremes of ontology are that there are no objects, or that every combination is an object. Until reading this I thought Lewis was in the second camp, but this sounds like object-nihilism, as in Van Inwagen and Merricks.
The one has different truths from the many; it is one rather than many, one rather than six [Lewis]
     Full Idea: What's true of the many is not exactly what's true of the one. After all they are many while it is one. The number of the many is six, whereas the number of the fusion is one.
     From: David Lewis (Parts of Classes [1991], 3.6)
     A reaction: Together with Idea 15521, this nicely illustrates the gulf between commitment to ontology and commitment to truths. The truths about a fusion change, while its ontology remains the same. Possibly this is the key to all of metaphysics.
A gerrymandered mereological sum can be a mess, but still have natural joints [Lewis]
     Full Idea: The mereological sum of the coffee in my cup, the ink in this sentence, a nearby sparrow, and my left shoe is a miscellaneous mess of an object, yet its boundaries are by no means unrelated to the joints of nature.
     From: David Lewis (Putnam's Paradox [1984], 'What Might')
     A reaction: In that case they do, but if there are no atoms at the root of physics then presumably their could also be thoroughly jointless assemblages, involving probability distributions etc. Even random scattered atoms seem rather short of joints.
An 'aggregative' sum is spread in time, and exists whenever a component exists [Fine,K]
     Full Idea: In the 'aggregative' understanding of a sum, it is spread out in time, so that exists whenever any of its components exists (just as it is located at any time wherever any of its components are located).
     From: Kit Fine (Things and Their Parts [1999], §1)
     A reaction: This works particularly well for something like an ancient forest, which steadily changes its trees. On that view, though, the ship which has had all of its planks replaced will be the identical single sum of planks all the way through. Fine agrees.
An 'compound' sum is not spread in time, and only exists when all the components exists [Fine,K]
     Full Idea: In the 'compound' notion of sum, the mereological sum is spread out only in space, not also in time. For it to exist at a time, all of its components must exist at the time.
     From: Kit Fine (Things and Their Parts [1999], §1)
     A reaction: It is hard to think of anything to which this applies, apart from for a classical mereologist. Named parts perhaps, like Tom, Dick and Harry. Most things preserve sum identity despite replacement of parts by identical components.
What exactly is a 'sum', and what exactly is 'composition'? [Harte,V]
     Full Idea: The difficulty with the claim that a whole is (just) the sum of its parts is what are we to understand by 'the sum'? ...If we say wholes are 'composites' of parts, how are we to understand the relation of composition?
     From: Verity Harte (Plato on Parts and Wholes [2002], 1.1)
If something is 'more than' the sum of its parts, is the extra thing another part, or not? [Harte,V]
     Full Idea: Holism inherits all the difficulties associated with the term 'sum' and adds one of its own, when it says a whole is 'more than' the sum of its parts. This seems to say it has something extra? Is this something extra a part?
     From: Verity Harte (Plato on Parts and Wholes [2002], 1.1)
     A reaction: [compressed] Most people take the claim that a thing is more than the sum of its parts as metaphorical, I would think (except perhaps emergentists about the mind, and they are wrong).
The problem with the term 'sum' is that it is singular [Harte,V]
     Full Idea: For my money, the real problem with the term 'sum' is that it is singular.
     From: Verity Harte (Plato on Parts and Wholes [2002], 1.1)
     A reaction: Her point is that the surface grammar makes you accept a unity here, with no account of what unifies it, or even whether there is a unity. Does classical mereology have a concept (as the rest of us do) of 'disunity'?
Classical mereology says there are 'sums', for whose existence there is no other evidence [Simons]
     Full Idea: Either out of conviction or for reasons of algebraic neatness, classical extensional mereology asserts the existence of certain individuals, mereological sums, for whose existence in general we have no evidence outside the theory itself.
     From: Peter Simons (Parts [1987], Intro)
     A reaction: Observing that we have no evidence for sums 'outside the theory' is nice. It is a nice ontological test, with interesting implications for Quinean ontological commitment.
'Mereological extensionality' says objects with the same parts are identical [Simons]
     Full Idea: Classical extensional mereology won't extend well to temporal and modal facts, because of 'mereological extensionality', which is the thesis that objects with the same parts are identical (by analogy with the extensionality of sets).
     From: Peter Simons (Parts [1987], Intro)
     A reaction: Simons challenges this view, claiming, for example, that the Ship of Theseus is two objects rather than one. I suppose 'my building bricks' might be 'your sculpture', but this is very ontologically extravagant. This is a mereological Leibniz's Law.
If there are c atoms, this gives 2^c - 1 individuals, so there can't be just 2 or 12 individuals [Simons]
     Full Idea: In classical mereology, if there are c atoms, where c is any cardinal number, there are 2^c - 1 individuals, so the cardinality of models is restricted. There are no models with cardinality 2, 12 or aleph-0, for example.
     From: Peter Simons (Parts [1987], 1.2)
     A reaction: The news that there is no possible world containing just 2 or just 12 individuals ought to worry fans of extensional mereology. A nice challenge for God - create a world containing just 12 individuals.
Sums are more plausible for pluralities and masses than they are for individuals [Simons]
     Full Idea: We are on stronger grounds in asserting the general existence of sums when considering pluralities and masses than when considering individuals.
     From: Peter Simons (Parts [1987], 5.2)
     A reaction: I was thinking that the modern emphasis on referring to plurals was precisely to resist the idea that we must 'sum' them into one thing. If so, we wouldn't want to then sum several plurals. If a mass isn't a sum, how can we sum some masses?
Sums of things in different categories are found within philosophy. [Simons]
     Full Idea: Cross-categorial sums are not unknown in philosophy. A body and the events which befall it are intimately connected, and the mysterious four-dimensional blocks might be mereological sums of the body and its life.
     From: Peter Simons (Parts [1987], 8.1)
     A reaction: Simons here ventures into the territory of abstracta, which he said he wouldn't touch. Presumably his first example has 'a biography' as its whole, which is not just a philosophical notion. Why will some categories sum, and others won't?
Collections have fixed members, but fusions can be carved in innumerable ways [Potter]
     Full Idea: A collection has a determinate number of members, whereas a fusion may be carved up into parts in various equally valid (although perhaps not equally interesting) ways.
     From: Michael Potter (Set Theory and Its Philosophy [2004], 02.1)
     A reaction: This seems to sum up both the attraction and the weakness of mereology. If you doubt the natural identity of so-called 'objects', then maybe classical mereology is the way to go.
Absolutely unrestricted qualitative composition would allow things with incompatible properties [Paul,LA]
     Full Idea: Absolutely unrestricted qualitative composition would imply that objects with incompatible properties and objects such as winged pigs or golden mountains were actual.
     From: L.A. Paul (In Defense of Essentialism [2006], §5)
     A reaction: Note that this is 'qualitative' composition, and not composition of parts. The objection seems to rule out unrestricted qualitative composition, since you could hardly combine squareness with roundness.