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Lecture

Week 8 Notes


Department
Philosophy
Course Code
PHLA10H3
Professor
William Seager

Page:
of 4
Philosophy Week 8 Notes
Sobers example adds depth to one of the principles
-one can be justified in believing P, even if P is not certain to be true
- sobers example suggests this principle:
One is justified in believing P if P is extremely likely to be true
The lottery ex. Shows that this principle will not generate knowledge
-if this principle is wrong, then how can we know anything, since almost all of our beliefs are not
absolutely certain to be true
-is the correct principle: one can be justified in believing P only if it is impossible for you to be wrong
about P
-this leads to the problem of scepticism
What is Scepticism?
-the philosophical position which asserts that we have no knowledge (various forms are possible)’
an argument for scepticism
1. we can know only what we can be absolutely certain of
2. we can be certain of (almost) nothing
3. therefore we know (almost) nothing
sceptics argue for their premises
-illusion argument
- dreaming argument
- brain-in-vat argument
We think we know a lot but what is wrong with simply assigning higher or lower possibilities to our beliefs
-instead of saying that I KNOW my name is, I can say I assign an extremely high probability to the
proposition ‘my name is
-but is my probability assignment justified?
-Scepticism might lead to the view that we have no more reason to believe P then to believe not-P for any
proposition
Descartes and Foundationalism
-Descartes used an architectural metaphor for knowledge
-To build a great tower needs very firm foundation
-Similarly, knowledge depends on foundation of propositions known as absolute certainty
Euclid’s two reasons
1.the axioms are ‘self-evidence
-- cannot be false
--are absolutely certain
2. the theorems follow from the axioms
- follow by pure logic
- inherit certainty
Descartes methods of Doubt
-use to discover the foundation of knowledge
- for any proposition, consider if there is any way (any way at all, no matter how weird) to put it in some (any at
all, no matter how small) doubt
- ex. Stephen Harper is prime minister
-Can we find a way to doubt this?
www.notesolution.com
-Easy it could be that he just died this second
- an indubitable proposition is one that passes Descartes test; it cannot be put into doubt
A posteriori beliefs
-Based on sense, memory and testimony
-Dreaming, hallucinating, and illusion give reasons for putting such beliefs into doubt
Basic sceptical argument based on the method of doubt
-Any proposition, P, is doubtful if there is a possible situation ( a P deceptive situation) in which that
proposition would seem to be true but would really be false
-We cant tell whether or not we are in a P deceptive situation, we might actually be in one
-If we are in one then P is false
-If P might be false, we don’t know that P
A priori beliefs based upon logic or mathematical reasoning
-Descartes evil genius argument
-Does it apply to utterly simple a priori propositions?
Are there any propositions that survive the acid of the method of doubt?
-Descartes thought this one did: I exist
-Any proposition which is such that if you think it, it must be true will survive the method of doubt
-Other ex.
oI am conscious
oNot :I see a dog” BUTI seem to see a dog”
-for any proposition you are inclined to believe, P
-just adding “it seems to be that P will give a doubt free proposition
Descartes mental Certainty
Descartes believe we could not be mistaken about our mental states (a thesis sometimes labelled the
incorrigibility of the mental – if we are in a mental state, X, we will know we are in X
-general incorrigibility and transparency do not seem very plausible
ounconscious mental states
oself-deception
but what about the current contents of consciousness as we experience them?
-could u right now be suffering excruciating pain and not know it? NO
-could you right now believe you are suffering excruciating pain and be wrong? NO
Clear and Distinct Ideas
Descartes wondered what made it the case that some beliefs could not be in error
ohe labelled the feature: clearness and distinctness
oclarity what is present and apparent to the mind
odistinctness every feature of the idea is clear
ex. The belief that there is a book in front of you
-this is not clear and distinct
-this idea involves (1) the experience of something to see a book and (2) the idea that the book is existing
in the world
-only (1) is clear and distinct
-it is what we can know for certaindirectly”
-the “rule of truth = whether we think of which is clear and distinct must be TRUE
www.notesolution.com
Descartes and mental Certainty
Mental certainty gives us a set of indubitable beliefs
-recall the architectural metaphor
oa foundation must be (1) solid
oa foundation must be (2) suitable for the building
maybe they are solid foundations, but are they extensive enough to rest all our knowledge on
-Descartes thought we needed to know that god existed
Descartes and God
If god exists (and created us and the world) but we are not able to know anything despite all the evidence before
us, then god would be a deceiver
-but god is no deceiver
-therefore, if god exists, we can know things (when we have good evidence)
-I think this means something like: if we have done everything we should about finding truth, then if we
are wrong, then it is someone else’s fault
-God has no faults however
-Note: connection to the problem of evil
How did Descartes prove god exists?
-causal argument (reacall the 1st two ways of Aquinas)
-my idea of god is of a perfect being
-there must be as much “perfection in these cause of an idea as there is represented perfection in the idea
itself
-therefore, the cause of god must be a perfect being=god
-Descartes used the word “objective reality” for what is represented in an idea (or picture)
Objective and Formal reality
- consider a picture of a horse
- the formal reality is what ever the picture is made out of (paper, ink etc.)
- objective or represented reality is a horse
-Descartes principle is that there must be as much formal reality in the cause of the picture as there is
objective (represented) reality in the picture
-A picture of a horse should be traced back to something like a horse
The problem here is that for a complex idea, we might construct the idea from simpler (and less perfect parts)
-the idea of god might be constructed from our ideas of limited knowledge, limited goodness and limited
power plus the idea of negation
-thus the idea of god=not limited power and not limited knowledge and not limited goodness
-we don’t have to trace this idea back to a single supreme being
-(Descartes denied this: he thought idea of infinity)
The Cartesian Circle
I need to know that the rule of truth is valid
- I can know this if I knew that a non-deciever god exists
- I can prove that god existswww.notesolution.com