PRINCIPLES OF
PHILOSOPHY
The Senses
Descartes now turns back to
his task of inventorying the mind for clear and distinct perceptions. He has
already told us what is clear and distinct in our perceptions of substances and
what is clear and distinct in our perceptions of principal attributes. What is
left now is to tell us what is clear and distinct in our perceptions of modes.
Sensation gives us the
ideas of many different properties in the world. It tells us that physical
substances have color, taste, smell, sound, heat, cold, pain, pleasure, size,
shape, number, and motion, just to name a few. But not all of these, Descartes
warns us, are really modes of physical substances. Color, taste, smell, sound,
heat, cold, pain, and pleasure (which are commonly known as "secondary
qualities") do not belong to physical substances at all. Though we think
that these properties exist out in the world, they are really only in our own
mind.
Descartes' proof for this
claim rests on the relationship he posited between a mode and a principal
attribute. A mode is just a determinate way of being a certain principal
attribute. The principal attribute of body is extension. Any mode of body,
then, must be a determinate way of being extended. Being square is a
determinate way of being extended. Being two feet by two feet by three feet is
another way of being extended. Being red, however, is not, nor is being sweet
or painful. No matter how you manipulate the properties of extension, you
cannot get out redness, sweetness, or the sensation of pain.
When talking about this
class of qualities (i.e. the secondary qualities as opposed to the primary
qualities) we must, therefore, be very careful if we are to avoid error. We
must always bear in mind that these sensations do not clearly represent
properties of bodies.
The discussion of primary
and secondary qualities concludes the inventory of the mind. We are now armed
with a method for attaining certain knowledge in all subjects, as well as all
the clear and distinct metaphysical ideas that we will need to draw upon in
this search for knowledge. We know that God exists and is perfect; we know that
the essence of mind is thought; we know that the essence of body is extension;
we know that mind and body are really distinct; and, finally, we know that
bodies are not colored, smelly, tasty, noisy, cold, hot etc., but that they are
shaped, sized, numbered, and motive. We are ready, in other words, to move on
to Book II, the principles of physics.
Analysis
Descartes' metaphysical
positions have not withstood the test of time very well. Very few people
believe that mind and body are distinct. Even fewer would ever use the concept
of a "substance" or an "essence" in trying to describe the
contents of the world. One of Descartes' positions, however, has been validated
by all subsequent scientific discoveries and remains a part of our modern
conceptual apparatus: the distinction between primary qualities and secondary
qualities. Advances in chemistry and physics have shown that we do, in fact,
live in a colorless, odorless, tasteless world—that these properties only come
into our picture because of our own physiology. Philosophers, reflecting on
this fact, have done a lot of work in trying to pinpoint what exactly this
means for secondary qualities. If secondary qualities only come into the world
because of us, does that mean that they only exist in our minds? Or does it,
rather, mean that they exist in the world but as an arrangement of atoms with
the power to cause certain sensations in us? Or do secondary qualities exist as
relations between the arrangement of primary qualities of objects and our
neurophysiology, relations that enable us to have sensations of secondary
qualities? The three views expressed in the form of these three questions are
referred to as "sensationalism," "physicalism," and
"dispositionalism," respectively. Given the importance that this
issue has developed, it is interesting to ask which of these three views
Descartes himself held.
There is evidence in the
text to support the claim that Descartes held any one of these views. In
principle I.68 Descartes says that secondary qualities should be,
"regarded merely as sensations or thoughts" rather than as,
"real things existing outside our mind." This sounds like a clear
statement of sensationalism. Descartes seems to be saying that the word
"red" does not refer to anything in the world. Instead, the word
"red" simply refers to the sensation we have of red. The mental state
does not represent red to us, it is red.
Backing a dispositionalist
reading of Descartes, is his tendency to refer to secondary qualities as
"dispositions." However, careful attention to the context in which
this word tends to appear, reveals that what Descartes is in fact referring to
in these passages are not relations between the arrangement of primary
qualities in objects and our neurophysiology, but, rather, the arrangements of
primary qualities themselves. These passages, then, actually support the view
that Descartes was a physicalist. Actually, this seems to be the most likely
reading of Descartes overall. Even in principle I.68, which starts out with
such a strongly sensationalist statement, Descartes concludes by saying that if
anyone examines the "nature of what is represented by the sensation of
color or pain … he will realize that he is wholly ignorant of it." If
color or pain is just our sensation of it, though, this statement would make no
sense. If red was just the mental state, then we would have a perfect
understanding of its nature. It is only if red is actually some property of
bodies, a property that does not resemble our idea of red at all, that we could
be wholly ignorant of the nature of red. An even more conclusive passage for
the physicalist reading comes in principle I.70. There Descartes seems to voice
the physicalist position exactly by saying that, "When we say we perceive
colors in objects, this is really just the same as saying that we perceive
something in the objects whose nature we do not know, but which produces in us
a certain very clear and vivid sensation which we call the sensation of
color."
REFERENCE
Descartes, Rene. Principles of
Philosophy. Trans. Valentine Rodger Miller and Reese P. Miller.
Boston: Kluwer Academic Publishers, 1991.
Descartes, Rene. The Philosophical
Writings of Descartes. Trans. John Cottingham, Robert Stoothoff,
Dugold Murdoch. New York: Cambridge University Press, 1985.
Cottingham, John, ed. The Cambridge
Companion to Descartes. New York: Cambridge University Press, 1992.
Des Chene, Dennis. Spitis and Clocks:
Machine and Organism in Descartes New York: Cornell University Press,
2001.
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