Lecture 7 Modality: Metaphysics of possible worlds Dr. Donnchadh O’Conaill (Donnchadh.oconaill@Helsinki.fi) 14/2/2017 406772 Metaphysics 2016-17 University of Helsinki

1. Introduction What are possible worlds? i.e., considering the metaphysics of modality To what are we committed when we say, e.g., ‘Necessarily, p’ or ‘Possibly, p’? Two options Possibilism: other possible worlds are possible but not actual entities Actualism: the only entities which exist are actual entities – we must find some way to accommodate possible worlds in the actual world

2. Possibilism Possible worlds nominalism is a reductive account of properties and modality in terms of sets of possible worlds: “it had better be possible to understand what possible worlds are independently of any reference to the things that get explained in terms of them” (Loux 2006 167) So how do we understand possible worlds? “It is uncontroversially true that things might be otherwise than they are. […] Ordinary language permits the paraphrase: there are many ways things could have been besides the way they actually are” (Lewis 1973, 84) …

“On the face of it, this sentence is an existential quantification “On the face of it, this sentence is an existential quantification. It says that there exist many entities of a certain description, to wit ‘ways things could have been’” (Lewis 1973, 84) What are these entities? Lewis: you know what the actual world is – a collection of concrete particulars Possible worlds “are more things of that sort differing not in kind but only in what goes on in them” (Lewis 1973, 85) – i.e., collections of concrete particulars

Possibilism: entities exist which are possible but not actual Just as real as the entities in the actual world, but not in the same spacetime What is the actual world? Lewis: whichever world it is in which an utterance (such as this one) is made The term ‘actual’ does not mark out anything ontologically distinctive: rather, it is an indexical, like ‘here’

Transworld individuals ‘It is possible that I didn’t study philosophy’: this is a true proposition Does its truth mean that I exist (not teaching philosophy) in a different possible world? Possibilist: no – rules out transworld individuals, individuals which exist in more than one possible world Such individuals would be identical but have different properties in different world…

Indiscernibility of Identicals Indiscernibility of Identicals: if a = b, then any property F had by a must be had by b, and vice-versa Transworld individuals violate this principle Suppose a exists in possible worlds W1 and W2 - a-in-W1will have properties which a-in-W2 lacks, and vice-versa – e.g., a studies philosophy in W1, not in W2 By the principle above, a-in-W1 cannot be identical with a-in-W2

3. Problems with possibilism Every individual is world-bound: an entity which exists in one possible world only Problem: how could things have been different for me? Since I exist in just one possible world, I could not have existed in one of the other ‘ways things could have been’ Undermines the reason for possible worlds Furthermore, every property I have is essential to me, i.e., a property I have at every world in which I exist

Counterpart theory Lewis: can explain de re modality by counterpart relation, relation of similarity between numerically distinct entities in different possible worlds “Your counterparts resemble you closely […] But they are not really you” (quoted in Loux, 171) Essential property: had by me and by all my counterparts in other possible worlds E.g., nothing could be my counterpart unless it was a person

Problems with counterpart theory “counterpart theorists are not giving us an analysis of our notions of essence and accident: they are changing the subject” (Loux, 180) I can feel relief or frustration that things didn’t go differently for me: this would make no sense on counterpart theory, since my feelings would be about someone else Likewise, I might have not studied philosophy – isn’t this truth about me, rather than about some other person?

Problems with modality Necessary proposition: for the possibilist, this is the set of all possible worlds Problem: on this view all necessary truths are identical, since each is a set with the same members Likewise with necessarily false propositions (‘Bachelors are married’, ‘Circles are square’) And with properties instantiated by the same individuals: e.g., ‘having three sides’ and ‘having three angles’

4. Actualism Actualism: the only things which exist are actual, i.e., in this world What are the other possible worlds? Plantinga: start with states of affairs, e.g., my being a lecturer, Paris being in France Abstract entities Like Platonic universals, states of affairs are necessary: can exist but not obtain My being a lecturer obtains; my being a superhero does not – but it does exist, i.e., it is part of the actual world

Actualism vs possibilism “a possible world is a possible state of affairs”: complete, cannot have more or fewer parts (Plantinga 1976, 144) Merely possible worlds exist in the actual world but do not obtain in this world Actual world is obtaining state of affairs “So A, the actual world, is an abstract object. It has no center of mass; it is neither a concrete object nor a mereological sum of concrete objects” (Plantinga 1976, 144)

An object is in a possible world = had this world been actual, the object would have existed Objects in the actual world: those which exist, given that this state of affairs obtains Essential vs accidental properties: entity x is necessarily F if for any possible world in which x exists, x would be F But can individuals exist in more than one possible world?

5. Transworld individuals Actualists: there are transworld individuals How about Leibniz’s Law? Distinguish: world-indexed properties: e.g. being tall-in-W1, where W1 is a possible world non-indexed properties: being tall The properties things actually have are non-indexed: i.e., John is tall, but also has property of being short-in-W1 – had W1 been actual, John would (actually) have been short No property that John both has in this world and lacks in W1

“How […] can a single thing be in several different worlds at once “How […] can a single thing be in several different worlds at once?” (Loux, 181) Plantinga: belief that there are transworld individuals is necessary for many common beliefs, e.g., “When I believe that things could have gone otherwise for me, I believe they could have gone otherwise for this very person” (181) “to say I exist in possible worlds other than this world is just to say that there are possible worlds […] which are such that had any of them been actual, I would have existed” (182)

Explaining transworld identity What makes objects which exist in different worlds identical across worlds? Essential properties? No – each of us shares the essential property of being a person Haecceity: individual essence, “a property such that the thing has it essentially and necessarily nothing other than the thing has it” (Loux, 182) e.g., property of being identical with Elvis Problem: do haecceities explain Transworld identity, or require it?

Next lecture: is time real?

Works cited Lewis, D. K. (1973) ‘Possible Worlds’ in Counterfactuals. Cambridge MA: Harvard University Press. Plantinga, A. (1976) ‘Actualism and Possible Worlds’ Theoria 42 (1-3): 139-160.