Meditation Two
Cogito Ergo Sum
Cogito #1
Cogito as Inference
□ (Ti→Ei). Not: □ (Ei)
Why this might be right
Thinking implies the existence of that which thinks
It is impossible to conceive that when there is
thinking going on, nothing exists. The Cogito
simply asserts this necessary connection between the
property of existence and the property of thinking in
anything capable of thinking.
Therefore, one can infer that “X exists” from the
truth of the claim “X thinks”, and this is the form of
the Cogito argument.
Cogito #2
Cogito as Performance
The act of thought by which I attempt to doubt my
own existence proves that I exist. (Jaako Hintikka)
Why this might be right
If the Cogito is an inference, it requires independent proof of a
buried premise, whereas if it is a performance, it does not, since it
is in fact a performance that proves the buried premise true.
Hintikka noticed that the truth of “I am thinking”
does not by itself establish the necessary truth of “I
exist”. As an inference, it seems to presuppose, in
addition to the first premise “I exist” another
premise: “I cannot think and fail to exist”. What
proves that to be true? The attempt to think otherwise. It is this act, this performance that proves one
cannot fail to exist when one is thinking.
How the Cogito Belief leads to a
Criterion for Absolute Truth
Ask: What does the Cogito have that all dubitable beliefs lack?
▪ Possible answers:
▪ 1. Clear and distinct ideas
▪ 2. Self-evidence
▪ Descartes’ proposal: if a belief contains, like the
Cogito, all and only clear and distinct ideas, and
seems self-evidently true to reason when it considers
it, then that belief is an instance of knowledge*.
Clarity & Distinctness &
Self-Evidence
What are they?
Clarity: obviousness. An idea is obvious if it is in
plain view. The idea is not obscured from view.
Distinctness: the idea cannot be confused with any
other idea.
Self-Evidence: A belief that is self-confirming (it
expresses what appears to be a necessary truth given
the concepts it contains...e.g., “A = A”).
The First Use of the Truth Criterion
The Proof that “I am a thinking thing”
I clearly and distinctly grasp that I am a thing that
thinks, and that if I were not to think, I would cease
to be what I am. Therefore, I know that I am a
thinking thing, and that I exist, and I know this
because this is a belief containing all and only clear
and distinct ideas, and that is self-evidently true to
my reason when I consider it (I cannot think that it is
false).*
*Note how ‘thinkability’ is doing a lot of work here.
The Nature of the Ego
Essentially: □ (Ti↔Ei)
It appears that here RD is giving the necessary and
sufficient conditions for “I”, and these appear to be
thinking and existing. This implies that when RD
says “Necessarily, I am a thinking thing”, he is
asserting both □ (Ti→Ei) and □(Ei→Ti).
If so, then □[(−Ti)→(−Ei)] (if I fall asleep, I cease to
exist!)
RD’s Possible Responses
1. Bite the Bullet
2. Bite the Bullet with Reasons (Karen Quinlan)
3. Deny that this is what he claims follows from “I know that I
exist as a thinking thing.”
What Jason Thinks About It
The relevant part of the Cogito biconditional that produces the apparent
problem, i.e., □ (Ei → Ti), should be modified to accurately reflect what
RD means in the Cogito. The Cogito assumes the Evil Demon Hypothesis,
i.e., the claim that thinking is going on and the Evil Demon is determining
its content (within limits we will discuss later in class). The Cogito asks
the epistemological question “what do I know given EDH?” It’s scope
cannot be the world since the world has been doubted away. Therefore, it
is not the ontological question “if I am thinking, does anything exist?” So
conditional should be written □(KEi → Ti), which means necessarily, if I
know I exist, then I am thinking. This bears no implication that in fact if
nothing is thinking, nothing exists. One clue to this interpretation is that
the EDH assumes there is thinking going on, yet the usual way of taking
the conditional drawn from the Cogito clearly considers a possibility ruled
out by EDH...that no thinking is going on. When faced with the proposal
that no thinking is occurring, the only appropriate implication is the
statement “then I cannot know that I exist”. This is a far cry from the
claim that nothing exists. It is even farther from the claim that when you
are not thinking, you do not exist. All the cogito supports is the conclusion
Has RD Forgotten the Role of Sense
Perception in our Discoveries about the
Wax?
No. We use our senses to get started thinking about the nature of
the wax. But when we are finished, we are using all and only ideas
that we could not have acquired through sense perception. Because
we could not get these ideas from sense perception, the beliefs we
form using thtem cannot be based upon sense perception.
Why Descartes thinks our ideas of extension cannot
come from sense perception: because they have
properties that ideas originating in sense perception
lack.
What Properties Are Those?
Consider the idea of a circle. How does it differ from particular
circles found in the world, ideas of which you can acquire by seeing
or touching them (RD calls these “adventitious ideas”)?
▪ The abstract idea of a circle as it is used in geometry, is a perfect
circle (unlike all actual circles we ever have seen or touched).
▪ No true proposition concerning circles could be either proved true or
proved false by pointing to some particular circle.
▪ Meno’s paradox of knowledge: You cannot acquire the idea of a
circle because any process by which you move from not knowing what
it is to knowing what it is requires you to be able to distinguish
between what is and what is not a circle, but to be able to do that just is
what it is to have the concept of a circle. To acquire the idea of a circle
from sense perception requires you to move from not knowing to
knowing the idea, and Meno’s Paradox shows this is impossible.
Why the nature of the Wax is known by
reason, not sense
Real properties of the wax, which we can and do know, are
infinitary, and sense perception cannot represent that which is
infinitary (we cannot “see or touch” infinitely many shapes, for
example, yet the wax has the capacity to take infinitely many
shapes, and this is one of its essential properties).
Comparison of this fact to the chiliagon case:
We know that a chiliagon has 1,000 sides, but we cannot see (with our eyes)
that a figure with 1,000 sides has 1,000 sides (not without counting them,
probably using a magnifying glass). The fact that reason can detect a property
that sight cannot present to the mind shows that reason is more acute about
extensional properties of objects, and that we must get the idea of a chiliagon
from sources other than sense perception (which is incapable of representing a
1,000-sided figure so that it is plainly different from a 999-sided figure).
The Plan of the Meditations
1. Use the method of doubt (EDH) to find a criterion for absolute
knowledge (by isolating some belief that cannot be doubted)
2. Use that criterion to discover some true beliefs that can be joined
in arguments that logically establish conclusions that defeat evil
demon skepticism skepticism.
How to do That:
A. prove God exists as the creator of the world and my mind and all
its powers. (Med. III)
B. prove that God is not a deceiver (is not an Evil Demon that
would mislead me in my belief-forming practices) (Med IV)
C. prove that all mathematical truths are instances of absolute
knowledge. (Med V)
D. prove that these truths describe the real nature of any possible
world consisting of bodies in space. (Med V)
What Devon Will Try to Prove
That Descartes has proved that any possible world must be one
consisting of extensional entities (bodies in space) if he properly
understands what he has shown in the wax argument. All the
arguments given later are redundant, or unnecessary to prove that
this is true, and knowable absolutely.
If Devon is right: Descartes wasted a lot of time
proving the existence of god, god’s nondeceitfulness,
the necessary truth of mathematics, and the existence
of a world of bodies in space in the meditations
following Meditation II.