Routledge History of Philosophy Volume IV

202 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
Next I examined attentively what I was. I saw that while I could pretend
that I had no body, and that there was no world and no place for me to be
in, I could not for all that pretend that I did not exist…. From this I knew I
was a substance whose whole essence or nature is solely to think, and
which does not require any place, or depend on any material thing, in order
to exist. Accordingly this ‘I’, that is the soul by which I am what I am, [ce
Moi, c’est à dire l’Ame par laquelle je suis ce que je suis] is entirely
distinct from the body…and would not fail to be whatever it is even if the
body did not exist. 82
It could be (and indeed was in Descartes’s own day 83 ) objected that merely
because I can think of ‘myself’ without thinking of my body, it does not follow
that I could really exist if my body were destroyed. After all, I may (if I am
ignorant of the real nature of gold) be able to think of gold without thinking of its
atomic structure, but it does not follow that something could still exist as gold
without that structure. Descartes’s position, however, is that if an object (in this
case the thinking thing that is ‘me’) can be clearly conceived of as lacking a
given property (in this case having a body), then that property cannot be
essential to the object in question.
The phrase ‘whose whole essence or nature is solely to think’ is the key to
Descartes’s reasoning here. Drawing on the traditional terminology of substance
and attribute, Descartes maintains that each substance has a nature or essence—
that is, a property or set of properties which makes it what it is. The standard
scholastic view (derived from Aristotle) held that there is a large plurality of
substances, but Descartes reduces created substances to just two categories: mind
and matter. The principal attribute of matter is extension (the possession of
length, breadth and height), and all the features of matter are reducible to ‘modes’
or modifications of this essential characteristic; thus a piece of wax, for example,
may take on a variety of shapes, but all these are simply mathematically
determinable modifications of res extensa, or ‘extended substance’. 84 But now,
just as all the properties of physical things are modifications of extension, so all
the properties of a mind (thinking, willing, doubting, desiring and so on) are all
modifications of res cogitans or thinking substance. And Descartes took it as
self-evident that the properties of thought and extension were not just different
but utterly distinct and incompatible. ‘On the one hand,’ he later wrote in the
Sixth Meditation,
I have a clear and distinct perception of myself, in so far as I am simply a
thinking, non-extended thing; and on the other hand I have a distinct idea of
body, in so far as this is simply an extended, non-thinking thing. And
accordingly it is certain that I [that is the soul by which I am what I am] is
really distinct from the body and can exist without it. 85