Atheism and Theism JJ Haldane - Common Sense Atheism
Atheism and Theism JJ Haldane - Common Sense Atheism
Atheism and Theism JJ Haldane - Common Sense Atheism
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202 J.J.C. Smart<br />
the restricted domain of classical mechanics, both the actual world <strong>and</strong> possible<br />
worlds would be lines in phase space. If I were a possible world enthusiast,<br />
I would (despite Lewis’s reservations) prefer to be an ersatzist. Plantinga has<br />
his own form of ersatz world, something which he calls a ‘book’ – a set of<br />
propositions such that for every proposition either it or its negation occurs.<br />
Suppose that we say that either ‘God exists’ or ‘It is not the case that<br />
God exists’ occurs in the book. Well, he doesn’t really exist if he exists only<br />
in the ersatz world (say, the book or a mathematical model). Surely in that<br />
case only the representation of God belongs to the ersatz world: ‘z exists in<br />
ersatz world w’ is a systematically misleading expression (as Gilbert Ryle<br />
might have put it).<br />
Most theists would prefer ersatzism to Lewis’s realism about possible<br />
worlds. Most theists believe that theism has something to do with morality,<br />
so that God would have an interest in whether I boil my gr<strong>and</strong>mother in oil<br />
or refrain from so doing. According to modal realism God should not be<br />
interested. If God creates all possible worlds (as I suppose a theistic modal<br />
realist would have to say), it does not matter whether I boil my gr<strong>and</strong>mother<br />
in oil or whether I don’t. In the set of real possible worlds there would be a<br />
world in which I do <strong>and</strong> another in which I don’t. A sufficiently hard-nosed<br />
Calvinist might respond by removing benevolence from his list of God’s<br />
excellences. After all the Calvinist view is that salvation is by grace not works,<br />
<strong>and</strong> people are predestined to heaven or hell, which does not sound like<br />
benevolence. Lewis is not a theist, but he avoids this worry about benevolence<br />
because he has a parochial interest in the actual world, just as an extreme<br />
nationalist might have no moral concern about what goes on in other countries.<br />
Lewis rejects H. Sidgwick’s wish to look on morals ‘from the point of<br />
view of the universe’ (for the modal realist the universe would contain all the<br />
real possible worlds). Still this is a digression in being an argumentum ad<br />
hominem to a certain sort of theist. We can discuss Plantinga’s argument,<br />
which refers to God’s excellences, whether or not we use moral predicates in<br />
defining excellence.<br />
The favourite modal logic system for propositional modal logic is<br />
C.I. Lewis’s system S5 <strong>and</strong> Plantinga’s is such a system in its propositional<br />
fragment. I shall, first, state Plantinga’s argument with reference to his possible<br />
worlds semantics for quantified modal logic (i.e. logic which countenances<br />
the words ‘possibly’ <strong>and</strong> ‘necessarily’ within the scope of words such as<br />
‘some’ <strong>and</strong> ‘all’). However, I shall go on later to state what I think is the main<br />
issue more simply in terms of propositional modal logic. Plantinga introduces<br />
the notion of a maximally great being <strong>and</strong> plausibly argues that maximal greatness<br />
implies maximal excellence. To be maximally great is also to exist in every<br />
possible world. Then he invites us to agree that a maximally great being is<br />
possible. Being possible it exists in at least one possible world, <strong>and</strong> being<br />
maximally great at that possible world it exists at all possible worlds.