Routledge History of Philosophy Volume IV

190 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
possibility of error, since the simple natures are ‘all self-evident and never
contain any falsity’. 18
Some of the simple natures are ‘purely material’; these include shape
extension and motion (and will be the building-blocks of Cartesian quantitative
science). But others, Descartes asserts, are ‘purely intellectual’, and are
‘recognized by the intellect by a sort of natural light, without the aid of any
corporeal image’; it is the intellectual simple natures which enable us, for
example, to recognize ‘what knowledge or doubt or ignorance is’. 19 Further, in
addition to the intellectual simple natures, there are what Descartes calls the
‘common’ simple natures, which include the fundamental laws of logic
(principles ‘whose self-evidence is the basis for all the rational inferences we
make’). 20 Using the basic rules of inference, we can make necessary connections
and so link the simple natures together to build up a body of reliable conclusions.
Descartes, though in the Regulae he goes into no details of how such reasonings
are conducted, provides some striking examples: ‘if Socrates says that he doubts
everything, it necessarily follows that he understands at least that he is
doubting’; or again, ‘I understand, therefore I have a mind distinct from a body’;
or again (most striking of all), ‘sum, ergo Deus est’—‘I am, therefore God
exists’. 21 These examples have an unmistakable resonance for anyone familiar
with Descartes’s mature metaphysics. The mind’s awareness of its own activity
and of its incorporeal nature, and the route from knowledge of self to knowledge
of God, were to be the central themes of Descartes’s metaphysical masterpiece—
the Meditations on First Philosophy (1641). But already in the Regulae we find a
recognition that these issues are an inescapable part of any well-ordered system
of knowledge. The intellectual simple natures, together with the corporeal simple
natures, comprise the two fundamental sets of building-blocks for human
knowledge (and, to preserve the metaphor, the common simple natures, or
logical rules of inference, are the cement which binds them together in the
appropriate relations). ‘The whole of human knowledge’, Descartes resoundingly
declares in Rule 12, ‘consists uniquely in our achieving a distinct perception of
how all these simple natures contribute to the composition of other things’. 22 The
materials, then, are ready to hand, Descartes seems to be telling us in his early
writings. The task of putting them together, of constructing a reliable edifice of
knowledge, remains to be undertaken. But it is already clear that this will have to
involve not just our mathematical intuitions about number and measure, but our
introspective reflections on our own nature as conscious beings. Descartes
claimed in his intellectual autobiography in the Discourse on the Method (1637)
that the task was one whose importance he realized in his early twenties.
Although he postponed its implementation, he knew that sooner or later a
metaphysical journey of self-scrutiny would have to be undertaken: je pris un
jour résolution d'étudier aussi en moi-même—‘I resolved one day to pursue my
studies within myself’. 23