Atheism and Theism 123one another, and a series whose members are intrinsically ordered as cause
and effect. To adopt Aquinas’s scholastic terminology, the first is a causal
seriesper accidens (coincidentally), the second a causal series per se (as such).
We can (perhaps) imagine objects, marked off by points in the number line
and receding to infinity, among which there are causal relations; but this is
not an intrinsic causal series. Contrast this with the situation in which each
object is an effect of its predecessor and a cause of its successor: but for object
−2, object −1 would not be, and but for object −3, object −2 would not be,
etc. Here it is essential to any item’s being a cause that it also be an effect; but
it is not necessary that they be temporally ordered, for in this case the terms
‘predecessor’ and ‘successor’ are not being used in an essentially temporal way.
That is what it means to speak of a ‘per se causal series’. Since the existence
qua cause of any item is derived from the causality of a predecessor there has
to be a source of causal power from outwith the series of dependent causes –
an ultimate and non-dependent cause.
If like Hume one denies that there is anything more to efficient causation
than regular succession, then the idea of real ontological dependence involved
in the definition of a per se causal series cannot be applied. It is an interesting
question to what extent those who deny the reality of causation are moved to
do so by a concern to block cosmological proofs. Certainly without causal
realism (and, I believe, the admission of a variety of causes) none of the
arguments I have been concerned with can work. As in the earlier discussions
of old and new style teleological proofs, however, I would defend such a
realism on anti-reductionist, anti-empiricist grounds independently of advanc-
ing a case for theism.
Someone might now reply that while there may be real causes, the proofs
assume and require more than this, namely that every event and object in
nature is caused. This brings me to the second objection which contends that
things may not always require an explanation; which is to say, that the prin-
ciple of sufficient reason or of adequate explanation is false, or at any rate
controversial. Hence it may be that a series of real causal dependencies term-
inates in a ‘brute cause’, a natural event that does not derive its existence or
efficacy from that of anything else.
Unless the question is to be begged, the fact that a principle is controverted
does not establish that it is controversial, in the sense of being open to serious
question. So anyone who wants to deny that contingent existence or natural
causal efficacy is derived from, and hence explicable by reference to some-
thing else needs to give reasons for rejecting what is a first principle of
enquiry: given something that is not self-explanatory look for an explana-
tion. Two such reasons are often presented. The first takes us back to Hume
who maintains that it is possible to conceive an object coming into existence
without a cause: