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tags:philosophy Possible Girls Modal Realism
Thesis
The world we live in is a very inclusive thing. Every stick and every stone you have ever seen is part of it. And so are you and I. And so are the planet Earth, the solar system, the entire Milky Way, the remote galaxies we see through telescopes, and (if there are such things) the bits of empty space between the stars and the galaxies.
But things could be different. Are there other worlds that are other ways?
Lewis advocates that there are, here in a thesis for a plurality of worlds Modal Realism.
There are so many other worlds, in fact, that absolutely every way that a world could be is a way that some world is.
Applications of Modality
This world is actual. That is one possible way for a world to be. Other worlds are other, that is unactualized possibilities. If there are many worlds, and every way that a world could possibly be is a way that some world is, and whenever such-and-such might be the case, there is some world where such-and-such is the case.
Modality turns into quantification “possibly there blue swans iff, for some world W, at W there are blue swans.”
NOTE
Supervenience - refers to a relationship between sets of properties or sets of facts. X is said to supervene on Y iff some difference in Y is necessary for any difference in X to be possible.
One’s moral character supervenes on one’s actions(s).
In philosophy of mind, many philosophers will make a general claim that the mental supervenes the physical. Mental properties of a person are supervenient on their physical properties If two persons are indistinguishable in all their physical properties, they must also be indistinguishable in all of their mental properties.
A person has a mental life of attitudes and experiences, and yet — perhaps! — all there is to him is an arrangement of physical particles, interacting in accordance with physical laws. Does the mental supervene on the physical?
- Narrow psychophysical supervenience: could two people differ mentally without also themselves differing physically?
- Broad psychophysical supervenience: could two people differ mentally without there being a physical difference somewhere, whether in the people themselves or somewhere in there surroundings?
Properties
We have frequent need, in one connection or other, to quantify over properties. If we believe in possible worlds and individuals, and if we believe in set-theoretic constructions out of things we believe in, then we have entities suited to play the role of properties.
The simplest plan is to take a property just as the set of all its instances - all of them, this- and other-worldly alike. Thus the property of being a donkey comes out as the set of all donkeys, the donkeys other worlds along with the donkeys of ours.
If we take properties as sets, so it is said, there is no distinguishing different but accidentally coextensive properties. But according to MR, these “accidentally coextensive” properties are not coextensive at all. They only appear so when we ignore their other-worldly instances. If we consider all the instances, then it never can happen that two properties are coextensive but might not have been.
Take Brownie, an other-worldly talking donkey. Brownie himself is, once and for all, a member of the set; hence, once and for all, an instance of the property. But it is contingent whether Brownie talks; Bronwie has counterparts who do and counterparts who don’t. In just the same way, it is contingent whether Brownie belongs to the set: Brownie has counterparts who do and counterparts who don’t That is how it is contingent whether Brownie has the property.
Isolation Islands
A possible world has parts, name possible individuals. If two things are parts of the same world, I call them worldmates. A world is the mereological sum of all the possible individuals that are parts of it, and so are worldmates of one another. It is a maximal sum: anything that is a worldmate of any part of it is itself a part. This is a consequence of the denial that worlds overlap.
For any two possible individuals, if every particular part of one is spatiotemporally related to every particular part of the other that is wholly distinct from it, then the two are worldmates. This formulation avoids difficults that might be raised concerning partial spatiotemporal relatedness of trans-world mereological sums; difficulties about multiply located universals; and difficulties about whether we ought to say that overlapping things are spatiotemporally related.
Suppose you discovered — say, from a well accredited oracle - that large parts of human history were re-enacted with interesting variations, in remote galaxies at times in the distant past and future. In speaking these re-enactments, you would surely introduce counterpart-theoretic comparisons of place and time. You might say that a remarkable event in one of them too place last year in Headington; when you would also say, without conflict, that it will take place a million years hence, lightyears away.
Worlds are also isolated in that there is no causation from one to another. Casual isolation is alongside spatiotemporal isolation as a principle of demarcation for worlds.
Actuality = this-worldly.
Quine is not a friend of possible worlds, ersatz or otherwise. But in “Propositional Objects” he briefly proposed that classes of ersatz worlds might characterise the attitudes of an animal without language.
Haecceitism
David Kaplan introduced as:
There seems to be some disagreement as to whether we can meaningfully ask whether a possible individual that exists in one possible world also exists in another without taking into account the attributes and behavior of the individuals that exist in one world and making a comparison with the attributes and behavior of the individuals that exist in the other world. The doctrine that holds that it does make sense to ask - without reference to common attributes and behavior - whether this is the same individual in another possible world, that individuals can be extended in logical space (i.e. through possible worlds) in much the way we commonly regard them as being extended in physical space and time, and that a common “thisness” may underlie extreme dissimilarity or distinct thisness may underlie great resemblance, I call Haecceitism… the opposite view Anti-Haecceitism, holds that for entities of distinct possible worlds there is no notion of transworld being. They may, of course, be linked by a common concept - as Eisenhower and Nixon are linked across two moments of time by the the concept of the president of the united states and distinguished at the same pair of moments, by the concept of the most respected member of his party, but there are, in general, many concepts linking any such pair and many distinguishing them. Each, in his own setting, may be clothes in attributes which cause them to resemble one another closely. But there is no metaphysical reality of sameness or difference which underlies the clothes. Our interests may cause us to identify individuals of distinct worlds, but then we are creating some - a transworld continuant - of a kind different from anything given by the metaphysics. Although the Anti-Haecceitist may seem to assert that no possible individual exists in more than one possible world, that view is properly reserved for the Haecceitists who holds an unusually rigid brand of metaphysical determinism.
Thisness. In essence, haecceitism focuses on the idea that each individual entity has a unique, unrepeatable quality that makes it different from every other entity. This quality is not dependent on an entity’s properties or relations to other things; it’s something intrinsic to the entity itself, which is “a set of principles which are essential to it and distinguish it from everything else.
Quidditism is to properties as haecceitism is to individuals.