1. Even if we assume that there is a deceiver, from the very fact that I am deceived it follows that I exist.
2. 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.
3. 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).
The Argument that the Mind is More Certainly known than the Body:
1. It is possible that all knowledge of external objects, including …show more content…
Therefore, every act of clear and distinct knowledge of corporeal matter also provides even more certain evidence for the existence and nature of ourselves as thinking things.
Therefore, our mind is much more clearly and distinctly known to us than our body.
I. Meditation Three: Descartes proves God's existence and that He is not a deceiver, thereby allowing us to be sure that we are not deceived when we perceive things clearly and distinctly.
A. Summary of things of which I am certain and those which I still must doubt.
1. I am certain that I exist as a thinking thing.
2. I must still doubt both my senses and my intuitions concerning mathematical knowledge since God may have constituted me so as to be deceived even about those things I seem most certain.
Therefore, in order to become certain of anything else I must inquire into the existence of God and see whether He can be regarded as a deceiver.
B. Preliminary Discussion of Ideas
1. I have ideas that are like images of things. The most common cause of error is the judgment that these ideas are similar to things that exist outside of me.
2. There are three possible types of ideas: innate, those that originate in myself, and those that originate from something outside of me. We shall be most interested in the latter …show more content…
Even though some ideas of apparent external objects come to me against my will, I cannot regard them as corresponding to external things. This is because:
a. I may have some faculty which produces these ideas.
b. Even if they come from outside me, I have no guarantee that they are similar to their causes.
Therefore, the principle upon which I have judged my ideas to be similar to external objects seems to be mistaken.
C. The argument for the existence of God from the fact that I have an idea of Him.
1. Besides its formal reality, which accounts for its mere existence as an idea, every idea also has objective reality according to the reality of the thing which it represents, or its object.
2. There must be as much reality in the cause as there is in the effect. This applies to objective reality as well as formal reality.
3. I need not assume a cause greater than myself for any of my ideas of corporeal substance nor of other people or angels.
4. I have an idea of a perfect God, and this idea has more objective reality than any idea of a finite substance.
5. The idea of God could not have originated in me, since I am a finite substance.
Therefore, God must exist as the only possible cause of the objective reality found in my idea of Him.
D. Objections to the argument and