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French philosopher, mathematician and
physical scientist (optics, physics, physiology)
Father of Modern Rationalist Philosophy
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Initiates intellectual break with ancient and
medieval thinking
Appeals to analytical reason and logic to investigate
the nature of both mind and nature in the context of
developing science
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Copernicus (Polish; 1473-1543)
 Astronomy: Heliocentric solar system
 Challenge to Church-endorsed Geocentric universe
Francis Bacon (English; 1561-1626)
 Development of the scientific method
Galileo (Italian; 1564-1642)
 Mathematician, Physicist & Astronomer; Copernican; challenge
to Church
Kepler (German; 1571-1630)
 Discovered laws of planetary motion
Boyle (Irish; 1627-1691)
 Developed experimental chemistry; worked in mechanics,
medicine, hydrodynamics
Newton (English; 1642-1727)
 Fundamental laws of physics; classical mechanics
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Is the mind different from
matter?
 Should we adopt the scientific
method to advance knowledge?
 What can we know with
certainty?
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Two Kinds of Substance
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Material Substance
 Essence = to be in space without thinking
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Mental Substance
 Essence = to think without being in space
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Pin Cushion Model of Object
Substance
 Attributes (forms)
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 Essential
 Accidental
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Bind and Unify Attributes
Persist through change
Individuate similar objects
Serve as the subject of thought
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Constitute qualities and relations
of objects
Bases of similarity and difference
among objects
Fluctuate in Change
Elements recognized in sensation
and thought
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Essential
Loss = destruction of object
 Determine objects kinds, types,
categories, genus or species
 Critical to our understanding of the
object (triangularity of triangles)
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Accidental
Fluctuate in change consistent with
persistence
 Not critical to our understanding of
the object (the color of a triangle)
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Conceivability
I can conceive of my mind as existing
only if I also conceive it as thinking
 So, thought is an essential attribute of
my mind
 But I can conceive of my mind as
existing without an extended body
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Hence, extension and body are not
essential to the mind
 Hence, it is possible that the mind
exist without a body
 Hence, the mind must be a different
substance from the body. Dualism
must be true!
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It is a mistake to infer from the fact
that body is not essential to mind
that the mind cannot exist without
a body
My mind may not need my body to
exist, but it needs some body to
exist
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Contrast: Triangles do not have color
among their essential attributes. But
every real triangle must have some
color or other. Perhaps minds are
related to their bodies in the way that
triangles are related to their colors.
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Since we do not think that dualism
with respect to triangles is true,
neither need we say that dualism with
respect to the mind is true.
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All Thoughts and ideas are
Intentional
 I.e. Ideas are About things that are
typically real things but which can be
nonexistent things
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Some thoughts and ideas are
Conscious
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It is inconceivable, and hence
impossible, that selected material
objects such as rocks are
intentional or conscious.
Hence, there is nothing in matter
that allows for intentionality or
consciousness
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Hence, intentionality and
consciousness can only occur in
something that is immaterial.
Hence, dualism is true.
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It is true that rocks can be neither
intentional nor conscious
However, from that it does not
follow that no sort of material
object can be intentional or
conscious
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It seems possible that intentionality and
consciousness emerge from material
complexity that rocks lack but things like
brains have.
In that case, intentionality and
consciousness are not grounds for
endorsing dualism
However, this raises the question: are
artificial minds possible?
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Can fallible human beings, using only their
own intellectual powers, establish genuine
knowledge of what is universally and
necessarily true?
 For example:
 Knowledge of mathematical truths, laws,
principles
 Knowledge of natural general laws and
principles
 Eg: Heliocentric solar system
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Working definition of Knowledge = true belief
based upon evidential certainty
 Contrast true “lucky” belief vs. true certain
belief
 Certainty and evidence
 How much evidence does knowledge
require?
 Consider evidence as probability under
multiplication
 Consider knowledge as tall building
requiring a firm foundation
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Both Descartes and the Skeptic agree that
knowledge = true belief based on evidential
certainty
Both also agree that there are only two kinds of
evidence:
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Empirical [or A posteriori” (from the Latin: “from the
latter”)] evidence = evidence based upon observation
(sensation/perception)
A priori (from the Latin: “from the former”) evidence =
evidence based upon pure reasoning apart from
observation; provable from absolute truths knowable by
reason alone.
However, the Skeptic denies the possibility of
evidential certainty, claiming that neither empirical
nor a priori evidence admits of certainty
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Meditation I: Descartes' provisional
argument on behalf of the skeptic
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Sensation/perception does not provide evidential
certainty because of
 Illusion: hence, no knowledge of attributes
 Hallucination : hence, no knowledge of particular
existence
 Dream Hypothesis: hence, no knowledge of
existence of the universe generally
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Pure reason does not provide evidential certainty
because of
 Evil Demon hypothesis
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Hence, certainty is impossible
Hence, knowledge is impossible
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The Cogito
Cogito, ergo sum
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Hence, each person can be certain about
 His/her own existence
 His/her own current ideas (psychological states), I.e. the
content of his/her own ideas/story/theory about the
external world
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Such certainty is limited to “what is inside,” to “what
the inside ideas/story/theory says about the
external world”
This does not address the question as to the truth of
the ideas/story/theory
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Arguments for the existence of God and, hence,
against the Evil Demon Hypothesis
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Ontological Argument
Formal and Objective Reality
If God exists as the creator/designer of our minds,
then our ideas/theories of the external world
must be generally (probably) true.
This falls short of certainty, but is nevertheless
sufficiently evident for knowledge.
Objection to Descartes:
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The Cartesian Circle: To refute the Demon Hypothesis
by reasoning to the existence of God circularly
presupposes that the Demon Hypothesis is false. It begs
the questions!
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Evil Sophomores
Classification of present sensations
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What shade of red was that?
Unconscious ideas
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Rhymes: how did you do that?
Unattended Channel Experiment
Implicit Beliefs in competition with Explicit Beliefs
 Eg. Have you seen my glasses? Did you put them on the
kitchen table? Oh! Yes, of course, I did!
 More interesting: Video of Tamar Gendler and Eric
Schwitzgebel. We harbor attitudes (biases) of which we are
unaware that influence our behavior and are inconsistent with
what we explicitly and sincerely state our beliefs to be. See
Mahzarin R. Banaji’s for her research on implicit attitudes
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The Problem of solipsism
“solus” = Latin for “alone”
 Am I alone in the universe?
 Is evidence of other minds also evidence of artificial
minds?
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