Routledge History of Philosophy Volume IV

196 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
less perfect’. 52 What Descartes is in effect presupposing here is a theory of
causation that is deeply indebted to the scholastic philosophical apparatus which
it is his official aim to supplant. According to the scholastic conception, causality
is generally understood in terms of some kind of property transmission: causes
pass on or transmit properties to effects, which are then said to derive their
features from the causes. 53 And this in turn presupposes that certain kinds of
similarity relations hold between causes and effects—in the words of the
traditional maxim which Descartes is reported to have quoted approvingly, ‘the
effect is like the cause’. 54 This allegiance to traditional models of causality casts
a shadow on Descartes’s bold professions of novelty—his claim to be ‘starting
afresh’ in metaphysics. That might not matter in itself, had not the explicit goal of
the whole enterprise been to build on solid foundations by demolishing
unscrutinized preconceptions. Yet to read through the proof of God’s existence
in the Third Meditation is to be confronted with a positive barrage of traditional
technical terms (‘substance’ and ‘mode’, and terms denoting various grades of
reality—‘formal’, ‘objective’, ‘eminent’ and the like), whose application the
reader is asked to take as self-evident. The scrupulous caution and
methodological rigour which were employed earlier to establish the cogito
argument seem to dissolve away here. In short, when endeavouring to establish
the metaphysical foundations for his new science, Descartes seems unable to free
himself from the explanatory framework of his scholastic predecessors. 55
But even if the details of Descartes’s proofs of God are taken on trust, deeper
structural problems remain. The most serious is what has come to be known as
the problem of the ‘Cartesian circle’ which was first raised by Descartes’s own
contemporaries, notably Marin Mersenne and Antoine Arnauld. 56 The function
of Descartes’s proof of God is supposed to be to establish the possibility of
systematic knowledge. If a perfect God exists, then the intellectual apparatus
which he bestowed on me cannot be intrinsically inaccurate. Of course, I may
make mistakes from time to time, but this is due (Descartes argues in the Fourth
Meditation) to incorrect use of free will: I often rashly jump in and give my
assent to a proposition when I do not have a clear and distinct perception of it.
But if I confine myself to what I clearly and distinctly perceive, I can be sure of
avoiding error: ‘I shall unquestionably reach the truth if only I give sufficient
attention to all the things which I perfectly understand, and separate these from
all the cases where my apprehension is more confused and obscure’. 57 Provided I
keep to this rule, I can achieve knowledge of countless things, including, most
importantly, the structure of the physical universe—the ‘whole of that corporeal
nature which is the subject of pure mathematics’. 58 Now the problem, in a nutshell,
is this: if existence of a non-deceiving God has to be established in order for me
to have confidence in the clear and distinct perceptions of my intellect, then how,
without circularity, can I rely on the intellectual perceptions needed to construct
the proof of God’s existence in the first place? Descartes’s answer to this
challenge appears to be that the divine guarantee enables us to construct long
chains of scientific reasoning but is not needed to establish the premises needed