Transcript Descartes’ Skeptical Observations

Descartes’ Skeptical Observations
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1. Several years have now past since I first
realized how many were the false opinions
that in my youth I took to be true, and thus
how doubtful were all the things that I
subsequently built upon these opinions.
2. Whatever I had admitted...as most true I
took in from the senses...; however I noticed
that they sometimes deceived me.
Descartes’ Dreams and Demons
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3. This all seems as if I
do not recall having
been deceived by
similar thoughts in my
dreams. As I consider
these cases I see there
are no definite signs to
distinguish being awake
from being asleep.
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4. Suppose an evil
genius has directed his
entire effort to
misleading me. The
heavens, the air, the
earth, the colors,
shapes, sounds, and all
external things would
be nothing but
deceptive games of my
dreams.
Qualitative indistinguishability of vat
experiences and sense experiences.
VAT MAN!
Oh Drat, I’m a brain in a vat!
Cartesian Certainty
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At length I am forced to
admit that there is
nothing among the
things I once believed
to be true, which it is
not possible to doubt,
not for reasons of
frivolity...but because of
valid and considered
arguments.
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Med. II: Even if a
demon deceives me, “I
am, I exist,” is true
whenever I doubt it. No
perceptual experience is
required to obtain this
knowledge.
“My body exists” cannot
be known with
certainty. So I am a
thinking thing that may
have a body.
Non-sensory knowledge of body.
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This piece of bee’s wax: tastes sweet, smells
flowery; feels hard and cold, squeezes when I
press it, makes sound when I tap it. I hold it
near the fire: taste is gone; smell evaporates;
color changes, shape is gone; size increases,
makes no sound when tapped. Yet I know it
is the same wax. So my knowledge of the
wax is is an intuition of the mind occasioned
by (but not based on) perception.
Benedictus de Spinoza
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Method: Begin with
self-evident
metaphysical truths
and deduce
theorems implied
implied by those
truths, producing an
absolutely certain
science of reality.
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…[T]here cannot be
conceived one
substance different
from another,- that is,
there cannot be several
substances, but one
only.
Extension and
consciousness are
modes of one infinite
substance, God.
Leibniz (1646-1716)
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The concept of extension is derivative, the building
blocks of reality are psychic particles, monads.
Extension is a property of a collection of particles,
each of which is unextended.
Each monad is designed by God to mirror the
universe. They do not interact causally, but a preestablished harmony governs their behavior.
A human is composed of monads, the chief of which
is the soul.
Principle of sufficient reason. This is the best of all
possible worlds.
An Essay Concerning Human Understanding (1690)
John Locke’s Empiricism
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If by this inquiry into the
nature of the understanding,
I can discover the powers
thereof; how far they
reach;…and where they fail
us, I suppose it may be of
use with the busy mind of
man, to be more cautious in
meddling with things
exceeding its
comprehension; to stop
when it is at the utmost
extent of its tether; and to
sit down in quiet
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ignorance of those things,
which, upon Examination,
are found beyond the reach
of our Capacities.
To ask, at what time a man
has first any ideas, is to ask,
when he begins to perceive;
having ideas and perception
being the same things.
He that would not deceive
himself ought to build his
hypothesis on matter of fact.
Locke’s Causal Theory of Perception,
Truth, and Knowledge
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The perception of external objects and
events causes images (ideas) in the
mind; reflection on how the mind
responds to this data causes ideas of
another sort (belief, hope, fear).
A tabula rasa (without innate ideas)
acquires and sorts images, creates
abstractions, and utters propositions.
The Production of Ideas
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An apple has qualities
that produce the simple
ideas of red, sweet,
crisp; from which we
form the complex idea
of apple, which, when
compared with other
ideas, gives rise to even
more abstract ideas of
fruit, taste, and
nutrition.
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Only primary qualities
(extension, number,
figure, motion, solidity)
are real, inseparable
properties of objects.
Secondary qualities
(color, taste, smell,
sound) are produced in
our minds but do not
really exist out there.
Options in Modern Philosophy
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Dualism (Descartes)
Materialism (Locke*)
Occasionalism (Malebranche)
Idealism (Berkeley): Esse est percipi;
to be is to be perceived. There is no
such thing as (what philosophers call)
material substance.
The materialist world view.
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Physical objects
would continue to
exist even if there
were no minds.
Physical objects
cause ideas to arise
in our minds.
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Physical objects have
primary qualities and
secondary qualities.
It is impossible to prove
beyond all doubt that
the physical world
exists. Skepticism is
irrefutable (but it may
be ignored)
George Berkeley (1685-1753)
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My endeavors tend only to unite, and place in
a clearer light, that truth which was before
shared between the vulgar and the
philosophers: the former [holding] that those
things they immediately perceive are the real
things; and the latter that the things
immediately perceived, are ideas which exist
only in the mind. Which two notions put
together constitute...what I advance.
Idealism
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Things we call
substances are
really just collections
of ideas which
depend for their
existence on the
mind. Reality is a
community of
spirits.
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We perceive ideas,
so if we perceive
objects, objects are
ideas. If they
weren’t ideas, we
couldn’t perceive
them. Since ideas
are mind dependent,
so must objects be.
Refutation of Secondary
Quality Realism.
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Intense heat = pain. Pain is minddependent. \ Intense heat is minddependent.
Place cold left hand and warm right
hand in water. Is the water cool or
warm?
Reducing sound to vibrations implies
that sound is not heard.
Against Primary Quality
Realism
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Red and purple sunsetis the color in the
clouds? What is the
real color? Sunlight?
candlelight? Under the
microscope? Reducing
color to matter and
motion makes real color
invisible.
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Perceptual relativity
affects primary quality
perception as well.
How large is a Perseae
mite’s foot?
To a mite----medium. To
us------ tiny.
To a Sub-mite---HUGE!
David Hume (1711-1776)
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We find in our minds
impressions (direct
sensations) and ideas
(copies of impressions).
Meaningful ideas can be
traced back to the
impressions that
produced them. Ideas
without impressions are
meaningless (e.g.
substance, self, cause).
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Legitimate ideas refer
either to relations
among ideas (math,
logic) or to matters of
fact (always possibly
false).
The gazing populace
receive greedily, without
examination, whatever
soothes superstition,
and promotes wonder.
Cause and effect.
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Reasoning about matters of fact assumes
causal connections. But there are no
impressions of causality. Sensation discovers
only constant conjunction of event pairs (fire,
heat). Hence, custom or habit (not
knowledge) is the source of our belief in
causal connections. Experience only teaches us
how one event constantly follows another, without
instructing us in the secret connexion which binds
them together.
Immanuel Kant (1724-1804)
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What has hitherto been called metaphysics
cannot satisfy any critical mind, but to forego
it completely is impossible; therefore, a
critique of pure reason must be attempted.
All knowledge begins with experience, but not
all knowledge arises out of experience.
Impressions supplied by sensation are
structured by cognition. A Copernican
revolution in Philosophy.
Is Synthetic apriori knowledge
possible?
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Analytic statements:
Content of the predicate
is contained in the
subject. (Nuns are
female)
Synthetic statements:
Content of the predicate
goes beyond content of
the subject. (Nuns are
nice)
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Apriori knowledge:
Independent of sense
experience.
Aposteriori knowledge:
Dependent on sense
experience.
Noumena: Perceiver
independent reality.
Phenomena: Reality as
it appears to us.
Midterm Review
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Pt I. Matching. Match the
philosopher with his quote:
Thales, Democritus,
Parmenides, Heraclitus (wk
1),Socrates (wk 2), Aquinas,
(wk 3) Hume, Mill, Pascal,
James (wk 4)
Part II. Short answer.
1.Objection to piety definition
(Euthyphro)(2)
2. The Socratic Mission (2)
3.James- skeptical balance (4)
4.Religious ambiguity(3,4)
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Pt. III. Essay (a) teleological
(design) argument or (b)
problem of evil.
Part IV. Multiple choice
1. Definitions- libertarianism,
hard determinism,
compatibilism. 2. Problem of
evil as objection to argument
for God’s existence. 3. Why
Plato opposes prayer/sacrifice
piety. 4. Definition of “rational
agent.” 5. Why Mill thinks God is
finite. 6. Heraclitus’ main point.
7. Famous Socrates quote.