Further Reflections on Atheism 201there is no first moment or last moment of time. However, Anselm probably
would not have considered such a topology. Still, why could not even such
a sempiternal entity be thoughtnot to exist? I am inclined therefore to think
that Anselm thought of God as eternal, not sempiternal: that is, he thought
of God as outside space and time. Does this make us think of God as like the
number 9, or the square root of 2, or e or π? Being outside space and time,
God would have to be like Leslie’s ethical principle (FE pp. 26ff ).
3 Plantinga’s Argument^6
Some of the reviewers, as I said, thought that I might have acknowledged
that the development in modern times of modal logic has led to variants of
the ontological argument. I have allowed for a minimalist account of modal-
ity, as suggested by Quine’s essay ‘Necessary Truth’ (see FE pp. 37– 8). Thus
‘necessarilyp’ is assertible in a conversation between Smith and Jones if ‘p’
follows by first order logic from contextually agreed or background pro-
positions common to Smith and Jones. Similarly, with counterfactuals, ‘If it
were the case that p then it would be the case that q’is assertible if, given
the denial of pand making the necessary consequential adjustments to
background beliefs, then q follows by first-order logic from p together with
the contextually agreed background beliefs. Of course Smith and Jones will
probably not have an explicit knowledge of first-order logic but they can be
expected to know how to argue correctly in accordance with it. It is interesting
to see how even small children can learn to use words such as ‘can’, ‘must’,
‘possibly’, ‘might’. Full modal logic, on the other hand, has a ‘possible worlds’
semantics and is more questionable.
Plantinga’s elucidation of modality in terms of possible worlds supposes
that things can be in possible worlds other than the actual world. He rejects
David Lewis’s ‘counterpart theory’ in which you (for example) cannot be in
another possible world, but only a counterpart of you. I prefer counterpart
theory, for Lewis’s reasons, but this is not a matter very relevant to our
present concerns and so I shall go along with Plantinga’s preference for the
sake of argument. Plantinga also rejects Lewis’s realism about possible worlds.
According to Lewis, ‘actual’ is an indexical expression which a person in a
world uses to refer to the world in which he or she is and for Lewis there is
no special ontological difference between worlds. If I read him correctly,
Plantinga prefers to think of possible worlds as what Lewis calls ‘ersatz’
worlds. An ersatz world is something in our world that contains entities that
mirror things and properties and relations in the actual world, though their
combinations would differ from the way in which things in the actual world
are combined. A mathematical model could be such an ersatz world. Thus in