Descartes

1
Descartes Skeptical Observations

• 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.

2
Descartes Dreams and Demons

• 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.

• 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.

3
Qualitative indistinguishability of vat
experiences and sense experiences.
Oh Drat, Im a brain in a vat!
4
Cartesian Certainty

• 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.

• 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.

5
Non-sensory knowledge of body.

• This piece of bees 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.

6
Benedictus de Spinoza

• Method Begin with self-evident metaphysical
  truths and deduce theorems implied implied by
  those truths, producing an absolutely certain
  science of reality.

• There 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.

7
Leibniz (1646-1716)

• 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
  pre-established 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.

8
John Lockes Empiricism
An Essay Concerning Human Understanding (1690)

• If by this inquiry into the nature of the
  understanding, I can discover the powers thereof
  how far they reachand 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

• 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.

9
Lockes Causal Theory of Perception, Truth, and
Knowledge

• 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.

10
The Production of Ideas

• 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.

• 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.

11
Options in Modern Philosophy

• 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.

12
The materialist world view.

• Physical objects would continue to exist even if
  there were no minds.
• Physical objects cause ideas to arise in our
  minds.

• 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)

13
George Berkeley (1685-1753)

• 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.

14
Idealism

• Things we call substances are really just
  collections of ideas which depend for their
  existence on the mind. Reality is a community of
  spirits.

• We perceive ideas, so if we perceive objects,
  objects are ideas. If they werent ideas, we
  couldnt perceive them. Since ideas are mind
  dependent, so must objects be.

15
Refutation of Secondary Quality Realism.

• Intense heat pain. Pain is mind-dependent. \
  Intense heat is mind-dependent.
• 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.

16
Against Primary Quality Realism

• Red and purple sunset- is 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.

• Perceptual relativity affects primary quality
  perception as well. How large is a Perseae
  mites foot? To a mite----medium.
  To us------ tiny. To a Sub-mite---HUGE!

17
David Hume (1711-1776)

• 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).

• 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.

18
Cause and effect.

• 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.

19
Immanuel Kant (1724-1804)

• 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.

20
Is Synthetic apriori knowledge possible?

• 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)

• Apriori knowledge Independent of sense
  experience.
• Aposteriori knowledge Dependent on sense
  experience.
• Noumena Perceiver independent reality.
• Phenomena Reality as it appears to us.

21
Midterm Review

• 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)

• 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 Gods 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.