Commentary on Meditations
II and III
Indubitable Truths and the Foundation
-- "Sum res cogitans"
At the end of the last unit we left Descartes savoring his triumph over
the malin genie. He has used the joint methods of doubt and
analysis to find one truth which is indubitable -- that if he is deceived
he must exist. This is a particular version of the cogito --
Cogito ergo sum -- "I am thinking, therefore I exist." Descartes
claimed that if he could find such a truth he would have the Archimedean
point he needs. Archimedes needed such a fixed point to place a lever
with which to move the world. Descartes needed an indubitable truth to
serve as the basis or secure foundation for erecting the edifice of
knowledge. But surely this one truth, that I exist, is not enough. Nor
does Descartes stop here. Having established that he exists, he goes on
But I do not fully understand what this "I" is that must exist. I must
guard against inadvertently taking myself to be something other than I am,
thereby going wrong even in the knowledge that I put foreward as supremely
certain and evident. Hence, I will think again about what I believed
myself to be before these meditations. From this conception I will
subtract everything challenged by the reasons for doubt which I produced
earlier, until nothing remains except what is certain and indubitable.
I take this to mean that Descartes is going to start over and apply the
method of doubt (and the method of analysis) to the question of what he
is. He will start with what he formerly thought himself to be, and
subject that conception to those increasingly more powerful skeptical
hypotheses, until only what is certain about himself remains. This, then,
is the second application of the methods of doubt and analysis. The result
of this new application of the methods is that Descartes concludes that he
is a thing which thinks (sum res cogitans -- "I am a thinking
thing."). So, here is the second indubitable truth which Descartes
discovers. The first was that he exists. The second is that he is
essentially a thinking thing.
What does Descartes mean by this claim? 'Essentially' here means a
property whose presence is necessary for the continued existence of the
object. So, if a property can be taken away from something and that thing
continues to exist, then it is not a necessary or essential property.
Note that Descartes says: "Thought and thought alone cannot be taken away
from me. I am, I exist, that much is certain. But for how long? For as
long as I think -- for it may be that if I completely stopped thinking I
would completely cease to exist."
The claim that thinking is essential to my existence is a problematic
claim, especially when one moves from a moment to extended periods of
time. Philosophers like John Locke made much of these difficulties in
criticizing Descartes. (There is a joke which embodies this criticism
nicely. It goes like this. Descartes goes to a cafe and orders a cup of
coffee. The waitress comes by later, sees that his cup is empty and says:
"Monsieur, a refill?" Descartes replies: "Merci, I think not." -- and
disappears!) For the moment, however, it is more important that you get
an idea of what Descartes has in mind by essential properties. We will be
coming accross more of these shortly.
There are other things which he might be, like a body, or a gas
permeating the body, and so on, but he is not going to decide about those
things at this point. This paragraph (the last full paragraph on Pg. 8)
is of some importance. For it shows that Descartes is not reasoning in
the following way:
This, as it turns out is fallacious reasoning. While the principle that
two things which share all the same properties are identical is widely
accepted as true, being able to doubt and not being able to doubt are just
not the right kinds of properties - - they are in the category of what we
know about something rather than what something is. The fallacy is
demonstrated in the Stoic example of the masked man. It goes like this.
We are in a room. Into the room comes your father. I ask you if you
recognize him. You reply that you certainly do, no doubt about it. Your
father leaves. In the door comes a masked man. I ask you if you
recognize him. You reply that you do not. I ask if this is your father.
You reply that it could not be. For:
- I cannot doubt that I am a thinking thing.
- I can doubt that I am a body.
- Two things which do not share all their properties are not identical.
- I am not a body.
At this point the masked man removes his mask and it turns out that it is
your father. You simply did not recognize him with a mask on. This shows
that the second argument is fallacious, for it has true premises yielding
a false conclusion. The first argument, the one about which we are
concerned, has the same structure. So, it too is fallacious. Descartes
has sometimes been accused of committing this fallacy, but it is
reasonably clear that he does not. Descartes is not in a position to give
the proof that he is not a body here. The claim that he is essentially a
thinking thing is one important piece of that proof. He will collect the
other materials for such a proof as he goes. This is why the proof for
the real distinction between mind and body is put off until Meditation
- You saw your father and you could not doubt that it was him.
- You could doubt that the masked man is your father.
- Two things which do not share all their properties are not identical.
- So the masked man is not your father.
Descartes goes on in this paragraph (which continues on to Pg. 9) to
discuss the nature of thinking. I am a thinking thing so, what does it
mean to think? Notice how the faculties come in again in this analysis.
As he concludes that he is a thinking thing, Descartes says: "...I am not
admitting that I am anything more than a thinking thing -- that is a mind,
soul, understanding or reason (terms whose meaning I did not previously
know)." So, here is the faculty of reason and understanding being
associated with thinking. He then goes on to discuss what else he migh be
in terms of mental images -- we are now at the level of the imagination.
He rejects mental images as supplying any genuine information about
himself. The contrast between the information supplied by reason, and
that supplied by the imagination is as sharp as the contrast between the
information acquired in my waking life and that acquired in my dreams!
But having mental images is also a form of thinking. Descartes cannot deny
that he has these mental images, whether the images correspond to anything
in the world or not. This analysis of mental images allows Descartes to
extend thinking to include the senses. It might seem that sensing would
not be the same as thinking. One might think of sensing as receiving
information from the eyes, ears and other senses about the world, whereas
(by contrast) thining might be regarded as something the mind can do
without receiving information from the senses. But considering sensing as
just having mental images, and setting aside the question of whether these
mental images correspond to external realities, Descartes can think of
sensing as a form of thought. This analysis of sensing is significant in
that it allows many more truths to be included in the foundation than
would otherwise be the case. We will consider how this is so when we take
up "The Representation Theory of Perception." The result of Descartes
inquiry is that to be a thinking thing means a being which "...doubts,
understands, affirms, denies, wills, refuses, senses and also has mental
images." (Pg. 9)