An astute reader e-mails,
First, sometime ago I recommended John Bishop's Believing by Faith: An Essay in the Epistemology
and Ethics of Religious Belief . If you have yet to read the book, I would recommend his new article
on Faith in the Stanford Encyclopedia of Philosophy. You may be particularly interested in
sections 7-10.
Second, I do not know a great deal about possible worlds semantics, and am taking a great risk of embarrassing myself in questioning your argument that "Necessarily, something exists" - but I think
that I will take a stab at it!
I am assuming that "Necessarily something exists" = "In at least one possible world, at least one
thing exists." Is this correct?
No. The first sentence is equivalent to 'In every possible world, at least one thing exists.' In other words, there is no possible world that is empty: every world has at least one item in it. But this is consistent with there being no one item that exists in every possible world. Suppose every being is contingent, where a contingent being is one that exists in some but not all possible worlds. Then there would be no one being that exists in all worlds, and 'Necessarily something exists' would be made true by the fact that each world has something or other in it. But if there is a necessary being (defined as a being that exists in all worlds), then of course the sentence in question is also true.
1. Does not your argument depend upon the assumption of 'modal realism' - that all possible worlds
actually exist, a highly questionable assumption?
No, because I am using the 'possible worlds' language only as a façon de parler, a graphic and intuitive way of representing modal relationships which I find helpful. (Unfortunately, most of my readers are completely 'thrown' by it!) In other words, I could have stated the argument without mentioning possible worlds. Here is a partial schedule of intertranslation, where 'world' is short for 'broadly logically possible world':
X is a necessary being =df X exists in all worlds
X is a contingent being =df X exists in some but not all worlds
X is an impossible being =df X exists in no world
X is an actual being =df X exists in the actual world
(Note that if x is contingent, it doesn't follow that x is actual, nor conversely)
X is a possible being =df X exists in some world
X is essentially F =df X instantiates F-ness in every world in which X exists.
X is accidentally F =df X instantiates F-ness in some but not all worlds in which X exists
X is necessarily F =df X instantiates F-ness in every world in which X exists, and X exists in every world.
(Example: God is necessarily, not just essentially, omnipotent.)
Proposition p is necessarily true =df p is true in all worlds
P is contingently true =df p is true in some but not all worlds
And so on.
Now isn't that neat? The modal notions are explicated in terms of the familiar quantifiers of predicate logic. The schema facilitates modal reasoning. For example, if x is necessary, does it follow that x is possible? Yes, because if x exists in all worlds, then it exists in some worlds. If x is possible, does it follow that x is contingent? No, because if x exists in some worlds, that leaves it open that it exists in all worlds. If x is noncontingent, does it follow that x is necessary? No, because if it is not the case that x exists in some but not all worlds, it does not follow that x exists in all worlds: x might exist in no world.
You characterize modal realism as the doctrine that "all possible worlds actually exist." No philosopher maintains that every world is absolutely actual. There is only one possible world that is absolutely actual: all the rest are merely possible. Now there is a philosopher, David K. Lewis, who maintains that there is a plurality of worlds, all on an ontological par, and thus all equally real; but he denies that there is such a property as absolute actuality. For him each world is actual at itself, but no world is actual simpliciter or absolutely. I reject Lewis's view which could be called extreme modal realism. Almost everyone rejects it. Lewis's idea, which is both brilliant and crazy at the same time, is that modality can be reduced to purely extensional terms via definitions like the ones I gave above. But few follow him in that. The above definitions do not allow one to eliminate modality by quantifying over worlds, because the worlds in question are possible, and 'possible' is a modal term.
So, to answer what I take to be your question, my argument does not presuppose extreme modal realism. In fact, it does not require that we take any stand at all on what exactly possible worlds are. But I do presuppose realism to this extent: I asssume that modality is not merely epistemic. Thus the possibility that I be sleeping now instead of blogging is a 'real possibility' in that it is subsists independently of what I or anyone know or believe. It is not possible merely in the epistemic sense of 'possible for all I know,' but possible independently of what I know.
2. Does not your use of 'exists' in premises 4 and 5 treat it as, or assume that it can be used as, a
'real predicate' rather than merely a 'grammatical predicate' (B. Russell) - again a questionable if
not false assumption?
I discuss this is various articles and in my 2002 book A Paradigm Theory of Existence. I argue, among other things, that Russell's theory of existence, which is closely related to Frege's, is a complete nonstarter, wrong from the ground up. There is something on Russell's theory in Paul Edwards' Heidegger's Confusions: A Two-Fold Ripoff.
In 'possible worlds' lingo, we say things like this: There are possible worlds in which Socrates exists but is not the teacher of Plato. Now of course those worlds are all merely possible because we know (or reasonably believe) that in the actual world Socrates is the teacher of Plato. So what does it mean to say that Socrates exists in those worlds? Let W be a merely possible world. To say that x exists in W is to say that, had W been actual, x would have existed. A merely possible world in which Socrates is not the teacher of Plato is a world which is such that, had it been actual, then Socrates would have existed without being the teacher of Plato.
My correspondent continues with several more questions/objections which I don't understand. In any case the above gives us plenty to discuss.
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