Philosophy 1 Lecture Day 15
• Descartes rationalist project is to accept as scientific knowledge only what is revealed by
the light of nature.
• Descartes notes that using C & D as a criterion of truth has an important limitation.
• When he is not perceiving the things themselves, doubt can creep into his mind.
• He can entertain the possibility that God might have made him so as to be deceived about
the simplest things.
• To remove doubt he must determine whether God exists, and whether God could be a
• He is taught by nature that he has certain ideas which resemble other things:
1. They seem to be about other things because they arise against his will.
2. We naturally assume that the ideas resemble physical objects which are their
• But which has been taught by nature can be deceptive:
1. The ideas might be produced by myself and not by other things.
2. Many of my ideas do not resemble what I think causes them (the sun looks the
size of a dime).
• The formal reality of a thing is its existence independent of thought.
• The represented beings have objective reality to that degree:
1. The idea of a substance is more real than that of its qualities.
2. The idea of an infinite substance is more real than that of a finite substance.
• There are degrees of existence that are represented by the ideas with degrees of
• I am not the cause of myself
1. If I had caused my own existence, I would have made myself perfect
• As a finite substance, I have enough formal reality to be the cause of an idea of any finite
substance besides myself:
a. Of other human minds
b. Of non-human minds (angels)
c. Of physical objects • So, my having the idea of a finite substance other than myself doesn’t prove that such a
finite substance exists.
• I do not have enough formal reality to be the cause of my idea of God, a supreme, infinite
being which created all other things.
• Descartes features Anselm andAquinas:
a. It moves from having an idea of God to God’s existence
b. The inference is from the idea as effect of God as cause of the idea
• Descartes claims: the cause of an idea with a given degree of objective reality must have
at least as high a degree of formal reality.
• Besides causing any idea of himself, God causes the existence of anything that has such
• The idea of God is that of a perfect being.
• Aperfect being is infallibly avoiding error(so long as I use it properly)
• I fall into error because I have an infinite will which can accept anything as true,
including what is beyond the limits of my understanding.
• When I fall into error, it is no fault of God’s:
1. I should thank God for giving me even limited understanding
2. Although God could have made me error free, God made me in a way he knew
3. I am able to avoid error by retraining my judgment within the limits of my