An Outline of Descartes's
Meditations on First Philosophy
Descartes’ Arguments for Universal
Doubt and the "Cogito" Argument
(An Outline of Meditations 1,2)
The argument for universal doubt:
The dream argument:
I often have perceptions very much like the
ones I usually have in sensation while I am
dreaming.
There are no definite signs to distinguish dream
experience from waking experience.
therefore
It is possible that I am dreaming right now and
that all of my perceptions are false
The deceiving God argument:
We believe that there is an all powerful God
who has created us and who is all powerful.
He has in his power to make us be deceived
even about matters of mathematical
knowledge which we seem to see clearly.
Therefore:
It is possible that we are deceived even in our
mathematical knowledge of the basic
structure of the world.
Objections to the deceiving God argument:
We think that God is perfectly good and would
not deceive us.
Some think that there does not exist such a
powerful God.
The demon argument:
Instead of assuming that God is the source of
our deceptions, we will assume that there
exists an evil demon, who is capable of
deceiving us in the same way we supposed
God to be able
Therefore, I have reason to doubt the totality of
what my senses tell me as well as the
mathematical knowledge that it seems I have.
The Argument for our Existence (the "Cogito"):
Even if we assume that there is a deceiver, from
the very fact that I am deceived it follows that
I exist.
In general it will follow from any state of
thinking (e.g., imagining, sensing, feeling,
reasoning) that I exist. While I can be deceived
about the objective content of any thought, I
cannot be deceived about the fact that I exist
and that I seem to perceive objects with
certain characteristics.
Since I only can be certain of the existence of
myself insofar as I am thinking, I have
knowledge of my existence only as a thinking
thing (res cogitans).
I THINK, THEREFORE, I AM
Cogito Ergo sum
The Argument God Exists
In my mind I have a clear idea of a perfect
entity (God) and this idea has objective reality
• The idea of God could not have originated in
me, since I am a finite substance
The idea of a perfect God could not have come
from me as I am imperfect
Therefore:
• The idea of God must have originated from
that perfect Entity itself ( ie, from God)
Therefore:
God Exists
“The Mind-Body Problem”
It is possible that all knowledge of external
objects, including my body, could be false if I
am being tricked by an evil demon
However, I cannot be deceived about my
existence or my nature as a thinking thing(
because I know that I exist)
• Yet a Perfect God would not deceive us
Therefore:
• Therefore, what we perceive with our Reason
is Reality
• Outer Reality is different than the reality of
thought
• Thought– MIND
• Extension– MATTER
• Both of these originate from God because only
God exists independently from anything else
• All Knowledge of External Reality is in the Mind
Wax example:
• All the properties of wax that we perceive with
the senses change as the wax melts
• Yet the Wax remains “Wax” even though it looks,
feels and smells different
• We know that it is Wax through our mind, not
through our senses
The mind is superior to the body
Human Beings have the capacity to rise above
bodily needs and behave RATIONALLY