Routledge History of Philosophy Volume IV

DESCARTES: METAPHYSICS AND THE PHILOSOPHY OF MIND 191
FIRST PHILOSOPHY
In using the term ‘first philosophy’ to describe his fundamental metaphysical
inquiries Descartes meant to draw attention to the fact that he proposed to deal
‘not just with questions about God and the soul but in general with all the first
things to be discovered by philosophizing in an orderly manner’. 24 The discovery
of reliable first principles is effected by a characteristic technique which has come
to be known as the ‘method of doubt’. Descartes (though he was accused of
being one 25 ) is certainly no sceptic; he uses doubt purely as a means to an end, to
demolish unreliable ‘preconceived opinions’ and clear away the resulting rubble
in order to establish a bedrock of certainty. The strategy is sketched out in Part
Four of the Discourse on the Method, and developed fully in the First Meditation;
its point is neatly summarized in the Synopsis which Descartes had printed with
the first edition of the Meditations:
Reasons are provided which give us possible grounds for doubt about all
things, especially material things, so long as we have no foundations for
the sciences other than those which we have had up till now. Although the
usefulness of such extensive doubt is not apparent at first sight, its greatest
benefit lies in freeing us from all our preconceived opinions, and providing
the easiest route by which the mind may be led away from the senses. The
eventual result of this doubt is to make it impossible for us to have any
further doubts about what we subsequently discover to be true. 26
Although commentators often present Descartes as a revolutionary philosopher,
the technique of ‘leading the mind away from the senses’ had a long ancestry.
Augustine had compared the senses to a ship bobbing around on the ocean; to
achieve reliable knowledge (e.g. of mathematics), we have to leave the ship and
learn to walk on dry land. 27 The general theme goes back ultimately to Plato,
who insisted that the first step to true philosophical understanding is to move
away from the shifting world of sense-based beliefs. 28 Descartes begins his
metaphysics, then, with a traditional softening-up process. Drawing on classical
arguments for doubt (whose revival had been a major feature of renaissance
philosophy 29 ), he undermines our confidence in the senses as a source of
knowledge by pointing out that they sometimes deceive, and ‘it is prudent never
to trust wholly those who have deceived us even once’. 30 He goes on to deploy
the celebrated ‘dreaming argument’ (‘there are no sure signs by means of which
being awake can be distinguished from being asleep’) to cast a general doubt on
the reliability of the inference from sensory experiences to the existence of their
supposed external causes. In the first phase of this argument, particular
judgements like ‘I am sitting by the fire’ are impugned: any particular experience
may be a dream. In the second, more radical, phase, doubt is cast on whole
classes of objects: perhaps things like ‘heads, eyes and hands’ are all imaginary—
part of some pervasive dream. 31 The conclusion reached is that any science (such