Reply to Haldane 161at things in a space–time way. Consider a thing which did not exist before
timet 1 and exists until time t 2 when it perishes, that is, it contains no temporal
part later than t 2. (Note that here I am using ‘exist’, ‘contains’, etc. as tenseless
verbs.) Well, there is no temporal stage later than t 2 and no temporal stage
earlier than t 1. But might the temporal stage between t 1 and t 2 have not
existed? Or could we say that the t 1 to t 2 stage was necessary though perish-
able? If there were a suitable sense of ‘necessary’ (which I am querying)
perhaps we could have said this, but no doubt we would not have done so
because if there had been a temporal stage later than t 2 it would have been
very like the t 1 to t 2 stage, and would therefore have been necessary too. Thus
I think that I can agree with Aquinas that the perishable is contingent.
I doubt, however, whether everything that is contingent is perishable. What
about an instantaneous event for example? Also in my longer essay I raised
doubts about the necessity of Platonic entities. Of course Aquinas was talking
aboutsubstances. I do have some trouble with the Aristotelian notion of
substance, in so far as metaphysically I like to think of the world as a four-
dimensional space–time entity.^24 However, setting this aside, let me raise
some doubts about the Aristotelian and Thomist notions of substance which
are more properly related to some things which Haldane says in his essay.
I am indeed not clear how far an Aristotelian notion of substance could
be made to fit a scientifically oriented view of the world. Is an electron a
substance? Consider quantum statistics, in which one distribution of particles
is sometimes to be considered as the same state as another. Swapping over
two particles makes no difference. This makes such a particle unlike a
substance as traditionally conceived. One rough analogy would be a wave.
A wave in the sea is not constituted by the water: as the wave goes forward
the water under it is not the same. We could swap over two waves of the
same form without making any difference to the sea. Indeed, it wouldn’t
really be a swap, as it would be if we swapped over the actual water under the
waves. Again, another analogy might be the idea that what exist are just
space–time points and field strengths characteristic of these points. I do not
want to press this objection to Aristotelianism and Thomism too hard, be-
cause I suspect that someone as familiar with these ways of thought as Haldane
is could reconcile talk of substance and attributes, potentiality and actuality
with the considerations that I have suggested here.
Haldane points out that what the traditional arguments for the existence
of God should be taken as proving is the thatnessnot the whatness of God.
There must surely be some whatness in what is proved. To prove the existence
of a something I know not what is hardly to prove the existence of anything.
However, it does resonate with the expressions of yearning by some anti-
dogmatic church-goers. ‘I feel that there must be something.’ This ties up with a
feeling that an atheist can have: a feeling of the evident ultimate mysteriousness