'It's logically possible that...'

We hear a lot about logical possibility - as in "it is logically possible that…" - in contemporary analytic philosophy. For example, David Chalmers says that it's logically possible that, zombies could exist. What do these claims amount to? Do they amount to much and should we be put out by them? Bertrand Russell thinks not:

"No logical absurdity results from the hypothesis that the world consists of nothing but myself… and that everything else is mere fancy. But although this is not logically impossible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the commonsense hypothesis that there really are objects independent of us, whose action on us causes our sensations." (Russell, 1912:22.)

When I wake up, it's logically possible that I'm still asleep. When I wake up, instead, it's logically possible that all my family are now dead. When I move over to the tap, it's logically possible that poison - not water - could come out of it. If it is water, it's logically possible that I could choke on the water. Then I look out of the window. It's logically possible that the town I see it a simulation of what I saw the day before. And so on.

I could think of ten logical possibilities before each breakfast.

But what is the point, even from a philosophical perspective?

Perhaps there's a big difference between the merely possible and the logically possible.

It's the logically possible that excites the sceptics and philosophers like Chalmers. Should I conclude - from all these logical possibilities - in the same way as Russell above? Should I say that "although [they are] not logically impossible, there is no reason whatever to suppose that [they are] true"?

Put simply. Something that's logically possible still may not be true. Indeed something that's logically possible probably won’t be true – won’t be the case. So why contemplate the logical possibility at all - even philosophically? Where will it get me?

Russell’s next point is that the logically possible hypothesis is (often?) "less simple" than the everyday one. He writes that "it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life". In my examples, this means that it's a less simple hypothesis to believe that I'm currently dreaming. It's a less simple hypothesis to assume that all my family is now dead. It's a less simple hypothesis to assume that poison will now come out of my tap rather than water. It's a less simple hypothesis to assume that my window-view is a mere simulation of the facts.

However, perhaps it doesn't really matter if my everyday hypothesis - if it is a hypothesis - is simpler than the logical possibility. Simplicity may not equal truth. A logical possibility may not automatically equal a falsehood. Perhaps the simplicity or complexity of each hypothesis simply doesn't matter to that hypothesis’s truth or falsehood. Perhaps simplicity is only psychologically appealing – and that’s it.

This is interesting because simplicity - or the simplicity of theories or hypotheses - is given a lot of credence in science – or so many philosophers of science have told us.

Russell, however, thinks that the simplest explanation is the "best". Thus:

"We can then ask: what is the best explanation of these experiences? Russell answers that the simplest explanation is the best; and the simplest explanation is the commonsense explanation. So we know that there is an external world because we seem to experience an external world; and the best explanation of our seeming to experience it, is that we really do experience it. Russell’s argument is an instance of the form of argument known as abduction, or inference to the best explanation." (Chappell, 79)

Again, why is the simplest explanation seen as the best? Is there a necessary - or logical - relation between simplicity and truth? Certainly many philosophers and scientists have thought so. Why? Because simplicity is more aesthetically appealing? In that case, what is the logical - or necessary - relation between aesthetic appeal and truth?

The example of "the best explanation of our seeming to experience the external world, it that we really do experience it" (79) doesn't really seem like an explanation at all. It certainly doesn't seem like a philosophical explanation; let alone a justification of one’s belief that the external world really exists! The fact that I seem to be rich doesn’t make me rich. I seem to experience goblins when drunk; though that doesn’t mean that they exist. Indeed if I seem to experience goblins when sober, why should I assume that goblins really exist and not, instead, explain my experience in some other way? So, again, why is the simplest explanation the best explanation?

In addition, when we make an abductive inference, is it necessarily the case that it must be the simplest inference or explanation? That is: does 

abduction = inference to the best explanation? 

They're indeed often connected; though are they synonymous? Chappell gives his own example of why the simplest explanation may not be the true explanation:

"Suppose sixteen very similar murders occur in one city in one month. On the facts we have, the best (and simplest) explanation of the murders might well be that the murders were all committed by the same criminal. It obviously doesn’t follow that this explanation is true: there will be many facts that we are not explaining by this hypothesis, because we don’t know them." (80)

For example, eight of the murders might have been carried out by a "copycat killer" – or even fifteen of them. Perhaps two killers are working in conjunction. Perhaps because all the killings were done with a handgun, that may have something to do with the fact that a thousand handguns were found and sold in the city to a thousand people. Thus that’s why all the killings were handgun killings, not because they were all committed by the same person. 

Perhaps the fact that all the deaths were similar may turn out to be a false in the end. Someone who died of poisoning might in fact have gone on a mushroom hunt the day before.

What do we mean by "similar" as in "similar murders"? For example, aren’t many murders similar to each other anyway? For example, in New York I would guess that 90% of killings are done with handguns of some description. So all these murders will be similar. It doesn’t follow that they were all done by the same person. If there were no guns, perhaps most murders would be strangulations. Again, not every case of strangulation would then point to the same suspect.

Despite all these possible explanations, it's still the case that an inference to the best explanation may be, well, the best explanation:

"Inference to the best explanation is obviously a useful intellectual strategy, perhaps an indispensable one." (80)

Indeed the simplest explanation of every murder in every city in the last ten years would be that the same man committed all of them – all 100,000 of them! Actually, perhaps that wouldn’t be a simple explanation because we would need to explain how he found the time and the skill to kill 100,000 people! We could settle on the simple hypothesis that all these murders were carried out by the same gang. Surely that would be a simple hypothesis.

The problem with using inference to the best explanation as "a useful intellectual strategy" (80) - in these examples at least - is that innocent people may be convicted of murder simply because their committing the murders is the simplest explanation on offer. That doesn’t - or wouldn’t - mean that they actually did commit the murders! However, the simplest explanation may be useful in the sense that if this weren't an "intellectual strategy",  the detective - or indeed anyone in any walk of like - may be overburdened with data. Some of that data would of course be irrelevant or bogus. 

The problem, of course, is deciding which facts or data are irrelevant or bogus. Perhaps some complex pieces of data - or some complex facts - aren't irrelevant or bogus. Perhaps they're really explanatory or even true. Still, a detective - or anyone else - can't have all the facts. And even all the facts he knows can't be thoroughly accounted for. We need to select what we think is relevant. Perhaps the way to do this is to select the simple facts - or explanations - of the matter at hand.

Imprecise Linguistic Expressions vs. Precise Propositions

The popular and general Fregean (etc.) idea is that because no particular expression of a proposition is identical to that proposition, then a proposition must be distinguishable not only from a specific expression of it, but from all expressions of it.

The argument is usually that a proposition is distinguishable from a particular expression. However, perhaps the truth is that it is the sum of all possible linguistic expressions of it. That is, when all possible expressions of the proposition are in, then there's nothing left out. There's nothing else to say about it. And if there's nothing else to say about the ostensibly expression-independent proposition that hasn't been said by the sum of all its linguistic expressions, then perhaps there's no distinction between them at all. Thus abstract propositions may not even exist in the first place for them to be linguistically expressed.

Michael Dummett goes into detail as to why Frege believed that there is such a distinction between a proposition and its linguistic expressions – or, in Frege’s case, between a sentence and the ‘Thought’ which it expresses:

"[A thought is] not true for you and false for me, it’s not true at one time and false at another time." 

The idea being expressed here is that it may appear to be the case that a thought is true for me though false for you; or true now, though false tomorrow. However, that's only because its linguistic expression leaves something out. If expressions were more precise and more explicit, such things wouldn't be left out.

This leads us to the conclusion that the Fregean Thought itself is precise and explicit. It's strange that something ostensibly non-linguistic can be both precise and explicit at all. How can something abstract and non-linguistic be precise and explicit? What does it mean for an abstract thought or proposition to be precise and explicit? Surely only linguistic expressions can carry the requisite information that will allow a thought to be precise and explicit. How can it be precise and explicit without its – or any – linguistic expression? What would constitute its precision and explicitness?

I mentioned the expression’s lack of precision and explicitness. Dummett explains why this is the case:

"Those are sentences which contain indexical elements: “It’s very cold today” and so on. So he says rather vaguely, when such sentences are uttered, the sentence itself does not suffice to express the thought. The time of utterance, for example, enters into the expression of the thought." 

Why must we bring in thoughts or propositions into this argument? It is of course the case that my sentence

"It’s very cold today."

won't be true tomorrow. It may be hot tomorrow. So, yes, it's imprecise and not explicit enough. However, we needn't bring in a thought to make it explicit and precise. All we need to do is reformulate the sentence thus:

"Today, the 11th June, 2008, it is cold here in the Midlands."

That will be still true tomorrow. However, even then we'll be required to drop the word ‘today’ and write:

"On the 11th June, 2008, it was cold in the Midlands."

We don’t require a thought/proposition that's more explicit and precise.

Even if abstract thoughts do exist, who’s to say that they must be more precise and explicit that their expressions anyway? Perhaps the utterer simply didn’t think of the time, date and location of his utterance. Unless the thought has nothing at all to do with what the utterer was thinking at the time. In that case, why call it a ‘thought’ at all – simply call it a ‘proposition’? In that case, because propositions are often unequivocally seen as abstract, then they needn't be thoughts at all.

Here again, why must we automatically assume that the abstract expression (which is somehow expressed) is more explicit and precise than the expression itself? What on earth is making it more precise and more explicit if it has nothing to do with thought at all? How can it be precise and explicit without linguistic expressions and therefore the communication of information?

Dummett himself sees some of these problems. As Julian Baggini puts it:

"Dummett sees part of the difficulty in working out how we determine what the thought is, given that many utterances which express a thought are ambiguous." 

Are the expressions of the thought (if it exists at all) ‘ambiguous’, or do they simply leave elements out? This may be more an example of ellipsis than ambiguity. Pragmatically speaking, we always need to leave things out of our utterances.

For example, many people say "Thanks" rather than "Thank you"; "What?!" rather than "What was that?"; or "The train’s arriving soon" rather than "The trains arriving in ten minutes 45 seconds". There are numerous examples of this. Can we really say that they are ambiguous rather than just elliptical?

In any case, what does it mean to "determine what the thought is"? How c/would we do that? What would we be determining? If it's genuinely non-linguistic and abstract, how on earth can we translate it at all into something concrete and linguistic? People speak about the problem of mind and body interaction (or they did), what about the problem of the proposition-linguistic expression relation? How is that possible? How can such unlike things have any kind of relation at all? In addition, when we get the thought or proposition right (or wrong), how do we know that we've got it right (or wrong)? We may have something more precise and explicit than any given expression. Though have we still got the proposition (or thought) wrong or right? How would we know? What is it, exactly, that we're getting right or wrong? How do we know that our utterances are "ambiguous"; or, for that matter, that they leave vital information out?

Perhaps all this ostensible ambiguity points to the fact that there's nothing to be ambiguous about. If we're ambiguous at all, it's simply because we haven't expressed what it is that we want to express. It may have nothing to do with the fact that we simply haven’t got the proposition (or thought) right. If we can’t know that we have it right (without the help of a philosopher like Dummett), then how do we know that we have got it wrong? And if we can’t know whether our expression is either right or wrong, then to speak of ‘right’ or ‘wrong’ in the first place may be suspect (to use an idea of Wittgenstein). In other words, there may be no proposition (or thought) to get right or wrong. There may be no such things as propositions or thoughts. The only thing we get wrong is saying something unclear or saying something we didn't really want to say.

We can’t really use the phrase  "What we want to say" because that would presuppose the existence of a thought that we wanted to express correctly. Perhaps we only know we've gone wrong somewhere when we don’t communicate properly with either ourselves or with another person. That has nothing to do with the expression somehow matching the thought or proposition. If anything solves the problem of inadequate communication, it will be another linguistic expression, not a thought. That is, an expression which effectively communicates what it is we want to communicate.

What it is we want to communicate isn't a thought or proposition at all: it's a satisfactory linguistic expression. The fact that we've gone wrong is a fact about our linguistic skills: not a fact about not matching an abstract thought or proposition. If we match our failed expression with something, it will be with other linguistic expressions which manage to communicate something more effectively. These alternative linguistic expression won't achieve this feet simply by being faithful to an abstract proposition. They'll do so only if they help us effectively communicate with ourselves or with other persons.

We must apply Occam’s razor here and simply get rid of propositions – we don't need them. We shouldn't posit more entities than we require. The only entities we do require are other linguistic expressions: not abstract thoughts or propositions. Why over-populate the "ontological slums" with yet more abstract entities when we don’t even require them in the first place? If we require objectivity and determinacy of sense or meaning, perhaps we can achieve it by comparing sentences with sentences so as to adopt the sentences which do the jobs which we want them to do.

In any case, something abstract and non-linguistic can hardly do the job of giving us more determinacy and objectivity if - by Dummett’s own lights - it's "difficult to work out how we determine what the thought is". If that's the case, then why do philosophers believe that things that are hard to determine somehow miraculously assure us of (more) determinacy and even objectivity? If anything is objective, it's a linguistic expression itself and the concrete objects they're often about. Abstract entities like propositions or thoughts surely bring with them more indeterminacy, not less.

Not many people disagree with what the word ‘cat’ means. Not many people know what to make of abstract entities like propositions - let alone how we gain access to them. The problems we have had with Platonic Forms or universals should give us pause for thought. After all, these mysterious entities have given philosophers seemingly unsolvable problems for over two millennia. They explain a lot, sure, though only at the expense of our having to believe in mysterious abstract entities, which themselves were taken to secure truth (if not meaning), determinacy and objectivity. What the philosophers have offered us in order to secure objectivity and determinacy has come at a price. That price is a belief in mysterious non-spatiotemporal entities which somehow spread themselves across the universes and over time.

Externalism & Accurate/True Representations

What is the basic internalist position? John Heil writes:

"Descartes is imagining that your inner life could remain wholly unaffected while the world you changed dramatically…" 

This position seems quite counterintuitive. One can immediately see how the "evil demon" and the "brain-in-a-vat" hypotheses immediately follow from this position. Quite simply, such hypotheses wouldn't be possible if the Cartesian position weren't true. It's almost as if one’s mind is a closed cell in which the only access to "external reality" is through a TV screen which nevertheless doesn't allow any direct causal content with the outside world. If that were the case, no wonder the world could radically change without the mind itself also changing. After all, if you watch a scene of war on your TV screen, you aren't really in that scene. Thus there is no need to run and there is no chance of you being shot dead – not even by a stray bullet. As Heil puts it:

"Both the demon possibility and the brain-in-a-vat fable assume that the contents of your thoughts about the world are a wholly internal affair. Your thoughts can have external causes, but their contents – what they are thoughts of – owe their character wholly on your internal constitution. Your thoughts about trees that are indistinguishable from thoughts about trees occurring to a brain in a vat or an agent under the spell of an evil demon." 

One can ask here that if the contents of our thoughts "are a wholly internal affair", then how can they be "about the world" at all? The world, on this picture, is seen as external, after all.

Even on the internalist picture we can accept that our "thoughts can have external causes"; though once they are caused, all that matters about such thoughts is their "internal constitution". That is, once they are caused we need no longer know anything about the world or its nature. Even thought these thoughts are indeed about the world, what the world is like now (or its causal interactions with the mind) simply no longer matter when it comes to knowing the contents of our own thoughts. The mind is disengaged from the world and no longer requires it when it comes to mental content and our knowledge of mental content. If the world no longer matters, then of course it's true that a brain-in-a-vat’s thoughts about a tree are indistinguishable from a brain-outside-of-a-vat’s thoughts about the same tree.

From the Cartesian thesis we directly get the brain-in-a-vat possibility. From the latter possibility we can say that of course there will now be a problem: "what reason could we have for believing that our thoughts about the world “matched” the world?" Because the world doesn't matter any more, and because our causal interactions with the world no longer matter (that is, because what the world does to the mind no longer matters), then of course we have a problem of matching up our thoughts with the world. If the world is no longer directly responsible for the contents of our thoughts now, then ‘"or all we know the world could be very different from what we take it to be". Not only that: there may not be an external world at all. Though if the world still matters, and if our causal interactions with the world still determine mental content, then it makes little sense to talk about the "external world" at all and thus these sceptical scenarios would no longer even occur.

What if we couldn’t have a thought about a particular tree if that tree were not causally interacting with us while we were having thoughts about it? If we require such causal interactions with the tree in order to have the thoughts that we're now having about it, then the sceptical hypothesis couldn't even arise in the first place. In order to have a thought about this tree, this tree must exist and must be causally interacting with us.

However, does it also follow that we are correctly matching or representing the tree’s shape? We may need causal interactions with the tree in order to have thoughts about it; though does it follow that what we think or represent correctly matches the shape or reality of the tree? Such causal interactions may bring these thoughts about; though it doesn't follow that our thoughts correctly represent the tree as it truly is. Causation alone doesn't seem to guarantee correct thoughts about the tree. It does, nonetheless, guarantee that we have thoughts about the tree of some kind.

Internalist Arguments Against Externalism

There are many problems with externalism.

For example, if narrow content doesn't completely encapsulate meaning, and we have to take into account our causal interactions with the world, then perhaps our beliefs will not fully cause our behaviour and instead those very causal interactions will do so instead. As John Heil writes: 

"… although Wayne and Duane’s beliefs play a part in determining what they do, their being beliefs – that is, propositional attitudes with definite contents – is causally irrelevant to their behaviour. Given the same stimuli, both will behave identically." (425)

If the meaning or the mental content is dependent on the world, or on causal interactions with the world, and meaning determines behaviour, then not only belief will determine behaviour – our causal interactions and the world will also do so.

Again, we may not be fully aware (or aware at all) of all our causal interactions with the world. Does this means that we don't fully know what we mean or even what we actually believe? Similarly, does this mean that we will not fully know (or know at all) how we will behave given a set of circumstances?
 
If how we behave is fully determined only by stimuli or our causal interactions with the world, then aren't we like machines or computers in that they too don't know the meanings of their input; just as, on this picture, we don't know fully the meanings of the sensory stimulations we receive and therefore the meanings of our mental contents or beliefs. Surely this would mean that we sometimes act in ways that we didn't know or predict we would act. We would be like thermometers which rise or fall without knowing why they rise and fall.

Heil puts the internalist objection to this position in this way:

"To the extent that an object’s behaviour is affected by its current state, how the object came to be in that state is irrelevant to how it comes to behave." (426)

What matters is not how we came to have our current mental state, or what causal interactions with the world brought it about; but the nature of the state itself. This is the internalist or Cartesian point. All that actually matters is the mental state as it is now, not how it was caused and not what caused it. The mental state itself is all we need to know and need to have access to. Only that, on this internalist picture, matters when it comes to our behaviour.

For a start, perhaps a vast array of things in the world might have brought about our current mental state. Not only that: perhaps historical factors dating back in time (perhaps indefinitely) were also partly responsible for my current mental state. Clearly we can't know all that is to be known about the aetiology of our current mental state. Perhaps we don’t need to know anything about any of the causes of it. That is the Cartesian position. However, if one is an externalist, it's important to know what causally determined our beliefs and therefore our behaviour otherwise we can't be in complete control of either our beliefs or our behaviour. Heil concludes:

"If you take externalism seriously, however, you will regard the contents of agents’ beliefs as being determined by historical factors. In that case, the contents of beliefs could make no difference to how agents’ behave." (426)

To the internalist, only narrow content matters. The externalist, on the other hand, believes that only wide content matters. To the internalist, the agent can indeed be completely unhooked from the world. To the externalist, we are thoroughly stuck (as it were) to the world. Or, more accurately, we are part of the world. There is no ‘external reality’. To know our beliefs or the mind itself is to know the world. To know the world is to know our minds or our beliefs.

If one is a naturalist, it will come as no surprise to say that we are part of the world. Of course we are! If we a part of the world, and there is no true ‘external reality’, then it's the case that scepticism about the existence of the world, or even about its nature, is thoroughly vanquished. Cartesianism or internalism itself creates the sceptical dilemma by completely separating mind from world. It does this, effectively, by proposing substance dualism. If internalism is rejected, then, so too is substance dualism. Thus agents can take there place as ordinary inhabitants of the world. Mind and world are brought back together. Indeed mind and body are also brought back together. We don't have souls after all.
 

Does Externalism Beat Scepticism?

John Heil says that instead of talking about different causal interactions between minds and world, why not talk about 'different contexts’: He writes:

"The face, located in a depiction of merry party-goers is a happy face. The very same face located in a scene of devastation and suffering is evil. The face’s being happy or evil depends, not on intrinsic properties of the face (or at any rate not wholly on these), but on the context in which the face appears. If you vary the context, you change the face." (424)

Again, the intrinsic properties of the face don't change whether or not it's seen as happy or seen as evil. The only things that change are the contexts. The change of context determines how we interpret the face regardless of the fact that the face hasn't actually changed at all.


This is clearly an analogous with what happens with the mind.


In both cases the Cartesian or internalist mind may not change. However, if the contexts of the minds or mind change, then so too does its mental content. More to the point, the change in context will determine and fix the meaning of the mental content. Though, again, neither mind is required to know that the context has in fact changed. Nevertheless, if it has changed, then it will change the meanings of the words and sentences expressed by such a mind or by such minds.


So meaning-in-mind depends on the mind’s causal relations to things outside of mind. And if that's the case, we can't really talk about ‘meaning-in-mind’ because meanings are partly determined or fixed by things outside of the mind. Perhaps we can't even talk, then, about the ‘outside’ of the mind or about ‘external reality’ if the so-called ‘internal’ reality wouldn't even be the way it is without an ‘external reality’. Perhaps the internal/external dichotomy simply breaks down, at least when it comes to talk about the mind’s relation to the world.


This, if it's true, is a sharp rebuke to traditional (epistemological) scepticism.


Why is that? Because scepticism "presumes a sharp division between our thoughts and the world of which those thoughts are directed" (424). As I've said, perhaps there would be no thoughts about the world if it were not for the world in the first place. More strongly, perhaps there would be no thoughts about X, Y and Z in the world , if X, Y and Z hadn't already determined or fixed these thoughts about themselves.


The sceptic asks us:

"What gives us the right to believe that what we think is the case is the case?" (424)

The externalist will simply answer:

"If the contents of our thoughts depend on how things stand in the 'external world', there can be no question of our being dramatically deceived." (424)

Our thoughts are determined or fixed by how things stand in the world. We wouldn't have these thoughts about the world if the things the thoughts are about didn't exist and they didn't have a causal effect on the contents of our thoughts (about them).


Does it follow that we can't be deceived?


Perhaps we can say that the world, or things in the world, do indeed determine or fix the contents of our thoughts. Does it follow, however, that our thoughts, or representations, correctly represent the way the world actually is even if the world has determined and fixed the content of our thought and has even given us these very thoughts in the first place?


We can accept this causal determination of mental content or thought; though causation in and of itself won't guarantee the correctness of our thoughts or representations of the world. As Davidson said (in a slightly different context): causation doesn't come under a description. Causation fixes or determines our thoughts ; though it doesn't determine their shape, as it were. It's responsible for mental content; though not for the shape of that mental content. Causation itself is neither thought nor mental content; just as it's not itself either description or explanation.


Why does it follow that because of the fact that we wouldn't have thoughts about the world in the first place if it weren't for the world itself, that how we think about - or represent - the world will be true of the world? Causal interactions can't be enough to silence the sceptic. All that we can say, however, is that there must be a world because we causally interact with it and those causal interactions determine or fix the thoughts or mental content; though they don't in and of themselves determine their shape.


The world must exist; though our thought and representations of the world may be radically inaccurate. Causation alone doesn't guarantee otherwise. Thus the sceptic is partly beaten in that the existence of the world is established. However, the externalist hasn't established the actual shape of the world. Perhaps this is a pyrrhic victory on the externalist’s part. Perhaps it's also a pyrrhic victory on the sceptic’s part.


The problem with these conclusions is that many, or all, externalists reject representations, or at least the idea of mental representations precisely because of their externalist position. The question is:


Why do externalists, and other philosophers of mind, deny the existence of mental representations?

De Re & De Dicto Modalities & Counterparts

A vital distinction in modal logic is the one between de dicto modalities and de re modalities.


The former apply to dicta – that is, statements, sentences, propositions, and the like. That is, it is sentences, statements and propositions that are necessarily true or possibly true.


De re modalities apply directly to objects in the world. Even if we use statements, sentences or propositions to talk about objects in the world, when we say that things are necessarily or possibly true of these objects ,we're talking about the objects themselves, not about the statements we've made about them. When we say that ‘horses are animals’ is necessary, the modality involved is de dicto. The sentence ‘Horses are animals’ is necessarily true. Thus it is, perhaps, a conceptual truth: the concept [horse] and the concept [animal].


When we say that


"Socrates is necessarily a person but only contingently a husband."


we'e talking about Socrates himself, not the statement about Socrates. One can see that the modal terms ‘necessarily’ and ‘contingently’ both occur within the actual sentence itself – necessity isn't applied to the sentence. The alternative version would be:


"‘Socrates is a person’ is necessarily true."


not


‘Socrates is necessarily a person.’


I said earlier that it is necessarily true that a world without animals is a world without horses. Now I can say that it is necessarily true that a world without persons would be a world without Socrates. However, it's not necessarily true that Socrates at a world must be a bachelor. That Socrates is a bachelor at our world is only a contingent truth. He, or his ‘counterpart’, may be married at least one other possible world. (If worlds are infinite, he must be married at an infinite amount of worlds and a bachelor also at an infinite amount of worlds.)


Could Socrates, our Socrates, really exist at any other possible worlds, let alone an infinite amount of them? Not according to David Lewis. According to Lewis, "individuals can each inhabit only a single world" (133). Socrates, then, only exists at one world – ours! However, I used the term ‘counterpart’ earlier. Lewis believes that our Socrates can, or could have had, counterparts at other possible worlds. More precisely, "to say that Socrates is possibly rich is to say that there is a possible world in which Socrates’ counterpart is rich" (133). This counterpart can be almost exactly like our Socrates. However, I think that there are arguments to the effect that he can't be identical to our Socrates. Lewis only accepts numerical identity. This means that if Counterpart Socrates were identical, he would be our Socrates. That would mean that our Socrates would exist at other worlds. Thus he would be a ‘trans-world individual’.


Lewis believes that these other worlds exist. It follows, then, that our Socrates couldn’t exist at any other world other than our own. An identical Socrates at other possible worlds would be a ‘scattered object’ – bits of him would exist, as it were, at other worlds; just as universals are multiply scattered in different locations and at different times.


Would it help the trans-world theorist to argue that Socrates is the sum of his ‘temporal parts’? If he can have spatial parts, perhaps he could also have temporal parts. Are these theses the same? We can say that Socrates at another world is one of Socrates’ temporal parts. Socrates at our world was another of his temporal parts. Socrates at our world in the future would be another temporal part of Socrates. And Socrates in the future of another world would be a temporal part of Socrates.


However, possible worlds aren't only causally disconnected, they're also temporally disconnected. Indeed, if we have causal discontinuity, then we would also have temporal discontinuity. Thus it makes no sense to talk either of temporal or spatial parts of Socrates at other worlds.


However, perhaps we can talk about the temporal and spatial parts of Socrates in our world. That would only be when he actually existed. That is, Socrates at the age of four would have been a temporal part of Socrates. Similarly with Socrates at the age of thirty. The sum of all his ages, before he died, would be the complete Socrates. Thus we would only know of the complete Socrates after his death. Four years before he died he would have been, as it were, incomplete! A minute before he died he would have been incomplete! The spatial discontinuity of Socrates is harder to accept because that spatial discontinuity could occur at the same time. Evidently temporal discontinuity can't occur at one and the same time. Of course we can have spatial discontinuity over time in that when he was four he lived in Athens, but when he was twenty he lived in, say, Islington.

Searle on the Presupposition of the World’s Existence

There are many anti-sceptical arguments which claim that the sceptic - of whatever kind - must assume and take as true certain things before he can offer us his sceptical possibilities or conclusions. Wittgenstein talked about the ‘hinges’ on which all discourse must turn - even sceptical discourse. Hume and Strawson believed that we must accept the existence of objects, other minds and even the existence of the ‘external’ world. Similarly, the premises on which both sceptical and paradoxical conclusions are built must be taken as true or even certain by the sceptic or paradox merchant.


John Searle talks specifically about the "presupposition of an independently existing" (185). He calls this 'a background presupposition". He says:

"It’s not something that’s up for grabs in the way that whether or not the human genome project will have such and such an effect is... I point out that it plays a certain role in our background presupposition, because it’s what we take for granted when we engage in discourse." (186)

This must mean that Searle thinks that even the global sceptic will take the existence of the world "for granted when [he] engages in discourse" (186). It seems, according to Searle, that he wouldn't even be able to say anything, or, more strongly, claim anything, if he didn't presuppose, perhaps tacitly, that the world actually existed. Perhaps he doesn't even know that he's doing this when he's doing it.


The very structure of language itself may include certain presuppositions as to the existence of the ‘external’ world. However, as I said about the meaning and the propositional attitude sceptic, the external world sceptic can't help but use the only language which he has. He has no choice but to do so. Perhaps the existence of God and Superman (as philosophers have argued) is written into our ‘ordinary’ and even our philosophical grammar. That doesn't mean that we are automatically committed to the existence of either God or Superman. It's simply a fact about our language and how it's structured.


Searle gives us a rather mundane example of a case of the presupposition that the world really exists:

"You and I made an arrangement to meet at a certain place at a certain time. We couldn’t make that and we couldn’t have our normal understanding of that unless we assume there is a place in space and in time that is independent of us and we can meet at that particular place. That is external realism." (186)

I don’t see immediately how it follows that because you and I arrange to meet at a place and a time that they must be ‘independent of us’. After all, I may be - or both of us may be - brains in vats fed by the same simulations.


Alternatively, on an idealist reading of Searle’s scenario, we can say that what he says happens could still happen if what the idealists claim is true. This place and time may just be mental ideas in our minds. Alternatively, they may be false sensory simulations given to us by an evil demon or a malicious scientist. According to the sceptic, the sceptical version would be identical to the non-sceptical scenario as far as our actual experiences are concerned.


So there doesn't seem to be any direct or automatic ‘presupposition’ of a mind-independent world here. In any case, not many people talk of - or even think at all about - the world’s mind-independence or its mind-dependence – that isn't the way people look at or think about the world.


So there needn't be either epistemological or ontological presuppositions involved when you or I arrange to meet somewhere at a place and a time.


Alternatively, if we arrange to meet at a particular building and unknown to us that building is just a facade from a film set, we still wouldn't assume that it's not a facade or, indeed, that it is a facade. Though it could be a facade. That wouldn't affect our meeting and what we thought about the meeting. (The street could also be a facade as well as having artificial traffic and human-like robots walking up and down it.)


Similarly, we could meet at this building at 6 O’ clock even thought it's 7 O’ clock when we actually meet. However, the clock on the building says it is 6 O’ clock and we think it is 6 O’clock because it says so. Not even that: it may well be 6 O’ clock when the clock says 6’ clock; though unknown to us that clock stopped three months ago and it's just a happy coincidence that it stopped at that time.


Again, none of this means that we need to assume the existence of the world and none of this has any impact on its existence or our knowledge of its existence.