234 J.J. Haldane
It is clear that the appeals are to experience of the world as the realist
conceives it. It is important to note, however, that some and perhaps all of
these arguments can be reconstructed even if that realist assumption were
unwarranted or false. Suppose, for example, that there were no external world;
or that it lacked the structure our concepts appear to attribute to it; or that all
we ever have access to are non-referential mental contents. It would still be
possible to pursue the via prima given that there is change in respect of these
last, with one idea or impression being succeeded by another. Similarly,
differences in modality and in degree of excellence are to be found within
thought itself; as I believe are differences in causality and in teleology.
Admittedly, however, these last claims are more controversial than are their
counterparts concerning what is found in the extra-mental world. Nonethe-
less, the general point holds good, which is that the traditional arguments can
be worked on the basis of idealism as well as of realism.
So far as I know, this fact has not hitherto been remarked upon, but it is
relevant to assessing the scope and power of an argument which has claim to
be Aquinas’s most original contribution to the search for theistic proofs, but
which does not feature in the quinque viae. In his Commentary on the Sentences
(II) Aquinas presents three arguments for the existence of God. The first is
teleological; the second is cosmological; and the third might be termed ‘onto-
logical’ – not because it is akin to the conceptual arguments of Anselm,
Descartes or Plantinga, but in as much as it arises from the idea that existence
is something additional to nature. Every thing (ens) is both a something and
an existent. Although these aspects are not distinct entities (either substances
or accidents) nonetheless they are real and are related to one another as
potentiality(or real possibility) and actuality(or actual existence). There are
two scenarios arising from this essence/existence distinction. First, the exist-
ence of a being might be implied by, and hence be metaphysically dependent
upon or identical to its nature. Second, essence and existence might be meta-
physically distinct. In the latter case the being or actuality of an entity is not
self-accounting but calls for explanation from beyond the thing itself. Gener-
alized, the question becomes that of how it is possible that entities whose
essences do not imply their existence nevertheless are actual. The answer can
only be that they participate in being (esse) through the action of some prior
actuality which is the efficient cause of their existence. The impending regress
can only terminate in an actuality that is self-subsistent: something of which,
uniquely, its existence belongs to its nature. And this is God, ipsum esse
subsistens.
This last expression has no easy non-philosophical form. We might speak,
transliterally, of ‘subsistent being itself ’, or of ‘pure being be-ing’, or of the
‘active existing of existence’. These formulations easily lend themsleves to
superficial parody of the sort sometimes directed against what William James,