Possible Worlds

By Michael Gakuran | | Philosophy | 4 Comments |


    Genuine Modal Realism (GMR)

Okay, so we’re no longer frightened by ‘Realism’ right? At least, not by the terminology. If you’re not sure, check here for a primer.

So what is Modal Realism? In a general sense, ‘Modality’ is talking about what is possible. What could have been, what could have been otherwise and what could never have been.

Philosophy has all sorts of fancy words for analysing the language we use such as ‘counterfactual conditionals’ (if-then; what would be the case), ‘verisimilitude’ (closeness to the truth – how one false theory can be closer to the truth than another false theory), ‘contingency’ (what could have been otherwise), ‘necessity’ and ‘impossibility’, among others. It’s not at all clear how to go about thinking of objects that ‘could have been’ or objects that are ‘necessarily the case’.

But what David Lewis, the proponent behind GMR, claims to be able to do is to provide a clear thesis to sort all of that out. In Philosophy, something clear and concise is not to be sniffed at. So what does he have on offer?

    There could have been

Lewis asks us to look at our statements of ‘what ifs’ and ‘could have beens’. Could we not try and think of possibility in another way? Take the statement I threw together here:

‘There might have been green crows’

Lewis asks us to think of this in terms of another possible world. The possibility of green crows existing is realised in another world.

= ‘There is a possible world with green crows’

By thinking of things in terms of possible worlds, it becomes a lot easier to understand propositions like ‘God necessarily exists’ (exists in all possible worlds) and ‘unicorns possibly exist’ (exist in some worlds), right through to trickier things like counterfactual conditionals. For example:

If Mike studies really hard, he will pass his Philosophy exam with flying colours

This simply means that there is at least one possible world where, from my studying really hard, I pass my Philosophy exam. Great! So even if I fail in this world, I can still say I passed in another! (questions of conscience as to whether I studied *really* hard aside…)

    Tenets of Modal Realism

Here I’ll outline the main theses behind Lewis’s GMR. It is worth noting that when we are talking of ‘worlds’, we are actually referring to is what we understand as the ‘Universe’.

Concretism – A world is the sum of all and only individuals related to one another spatially, temporally or causally. (e.g. our ‘Universe’)

Realism – Our world is but one of many possible worlds. All worlds and their individual parts exist and are all equally real.

Mind-independence – The other worlds and individuals in them are independent of us. We did not make them and they would exist irrespective of what we thought.

Parity – The individuals in other worlds are the same kind of thing as in our world, but they differ in content.

Isolation – No world nor individual in a world can be in any spacial, temporal or causal relation to any other world. I.e. if an individual is part of a world then it is part of that world only.

Plenitude – Every possibility is realised at some world. Furthermore, take any parts of any worlds and any spacial or temporal relations between those parts and there is a single world containing duplicates of all the parts in any arrangement (providing they are not too large, numerous or shaped awkwardly to fit) (recombination principle).

Actuality – Actuality is an indexical term (e.g. here, now, my) and so refers to the world of the speaker alone. Thus when we speak of the ‘actual’ world, we mean our world. (If a person in another world spoke of actuality, they would be referring to their world).

    Postulating pixies and other absurdities

Did you skim through the main points in Lewis’s GMR? Maybe not..? Talk of Cornish Pixies seemed much more interesting right? Why should we even go in for all this nonsense anyway? Why on earth believe a theory that tells us Cornish pixies concretely – they really do – exist? And not just that, unicorns, centaurs, seraphim and those curious vampire ducks with fins and fur that go moo in the night. They all really exist. How can we admit this??

The reason, argues Lewis, is that his theory best describes and illuminates on our picture of the world. Most people would agree nothing is ever black and white in Philosophy; there is always some counter-theory or wicked failing premise in your argument. It’s nearly always a case of one theory being more plausible than another, and largely the consensus of philosophers of the time.

And Philosophy is here to challenge what we take to be common sense. Of course, that’s not to say it’s job is always to refute what intuitively seems to be the case, but it seeks to remind us that our intuitions and common sense aren’t always correct. Science sometimes disproves what seems to be common sense (remember the time they all thought the world was flat?) Philosophy, similarly, challenges us to reconsider and think about the way we look at and interact with the world.

Thus, what Lewis is advocating is to do just that. His theory clears up all these problems with modal logic and gives us a clear way of thinking about things, or so he claims. The reason we should accept his theory is that he thinks the ‘benefits are worth the ontological cost’. Simply, in exchange for getting a theory that really helps clarify things (especially for Philosophers who dabble with modal logic), we have to admit things such as angels, unicorns and vampire ducks into our way of thinking about the world.

But are you willing to pay the price? It’s very important to note that Lewis’s theory isn’t talking about parallel universes or abstract objects. If we agree to accept it because it clarifies our thinking in many areas, we are paying a heavy price. We are forced to admit there *really are* vampire ducks and such that *really* exist in another world. Sure, we can never come into contact with them (thankfully), but are we prepared to admit they swim around mooing in some distant world?

And is that all..? Not by a long shot. Next we’ll take a deeper look at the problems in Lewis’s theory and seeing if we can’t get a better theory without agreeing to the existence of pixies and whatnot. Or maybe you want to. Worlds with pixies sound kinda fun.


Resources: Handouts from my lecturer, Dr. John Divers (writer of ‘Possible Worlds’ (2002)) and the book ‘Realism and Anti-Realism’ (2007) by Stuart Brock and Edwin Mares.

Page 1 – Realism and Anti-Realism – primer

Page 3 – Problems with Modal Realism

Page 4 – Ersatz Modal Realism

4 comments on “Possible Worlds
  1. Egmont says:

    Any word on whether he was talking about parallel universes, or simply other planets? Or did he not have physicality in mind at all?

    And how did he figure that this world we are in is the best of all possible worlds? I recall that from reading Voltaire’s Candide back in high school.

  2. Egmont says:

    Any word on whether he was talking about parallel universes, or simply other planets? Or did he not have physicality in mind at all?

    And how did he figure that this world we are in is the best of all possible worlds? I recall that from reading Voltaire’s Candide back in high school.

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