PHI 101 Chapter Notes - Chapter 13: Parallel Postulate, Foundationalism, Oedipus Complex
13 Jan 2017
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Chapter 13: Descartes’ Foundationalism
1. Foundationalism
a. Descartes wanted to show that the beliefs we have about the world are cases of
genuine knowledge
b. Two categories of beliefs
i. Foundational beliefs: perfectly solid
ii. Superstructural beliefs: count as knowledge because they rest securely on
that solid foundation
c. To show that a given body of beliefs counts as knowledge, we use first identify
the beliefs that will provide the foundations of knowledge
i. Must have some special property, such as being totally beyond doubt
d. Secondly, we show that the rest of our beliefs count as knowledge because they
bear some special relationship to the foundational items
2. Euclid’s Parallel Postulate
a. If you have a straight line (call it S) and a point not on the line, then there is
exactly one straight line that goes through that point and is parallel to S.
b. This assumption was much less obvious than Euclid’s other assumptions.
Geometer tried to show that it could be proved from other axioms, but they could
not
c. This shows that it isn’t so clear whether something is obviously true or not; Euclid
thought this was obvious but everyone else did not
3. Descartes’ Method of Doubt
a. For each proposition you believe, you see whether it is possible to doubt that
proposition. If it is possible to do this, you set the belief aside
i. It isn’t foundational
b. If it isn’t possible to doubt a belief, then it is foundational
c. Failing the method of doubt test doesn’t show that the belief is false. It just means
the belief isn’t absolutely certain
4. This Method Applied to a Posteriori Beliefs
a. It is possible to doubt these beliefs
b. The senses can be misleading
i. Illusions and hallucinations exist
ii. Dreams as well
5. Dubitability is a logical, not psychological, property
a. It has nothing to do with whether we can get ourselves to believe that the
proposition is false
6. The Method Applied to Beliefs Based on Rational Calculations
a. Do a priori beliefs fail this test?
i. Descartes says they do
ii. He asks us to imagine that our minds are deceived by an evil demon that
causes our faculty of reasoning to find propositions totally obvious in fact
are false
iii. If this is so, we might believe that 2 + 3= 4 even though that proposition
isn’t true
7. I am thinking, therefore I exist
a. This proposition is beyond doubt
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