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2. Metaphysics and Epistemology
Reality: What is real?
Knowledge: What is truth?
The usual (circular) assumption:
reality is what we know as objective existence in the world;
knowledge is what we know about reality.
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3. Epistemological Questions
Do we really know objective reality?
How do we know objective reality?
“Objective reality” = what is independent of what we think/feel…
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4. Sources of Knowledge
Where does knowledge come from? (experience or reasoning?)
Empiricism: All knowledge comes from experience (a posteriori).
Rationalism: All reliable knowledge (scientific laws, etc.) comes from rational deliberation (innate ideas + reasoning). (a priori)
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5. LOCKE VS. LEIBNIZ ON INNATE IDEAS
The Empiricist:
LOCKE: NO INNATE IDEAS
The argument from universal consent for innate ideas is inconclusive
Children and “idiots” do not have innate ideas; we are born with a mind as a blank tablet (tabula rasa)
It is impossible to have ideas of which we are not conscious
The Rationalist:
LEIBNIZ’S REPLY TO LOCKE
Sense experience alone cannot validate general principles or laws
There is extensive evidence that we have innate cognitive structures
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6. Rene Descartes’ Rationalism (Chapter 5, pp. 215-227)
Experience is not reliable:
The wax argument (is it the same thing after it melts?)
The dream argument
Only reason is reliable:
“I think, therefore I am.”
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7. The Empiricist: LOCKE’S CAUSAL THEORY OF PERCEPTION: ELEMENTS OF THE KNOWING PROCESS
The entity or object in the world
Sensations (sense data, images, sensory impressions) emitted by the objects via “impulses” and transmitted to our five senses
Ideas, which Locke characterizes as “the immediate objects of perception, thought, or understanding”—in other words, the images or impressions produced in our minds by the impulses emitted by the objects
The human subject, knower, or conscious mind who is able to perceive the ideas in his or her mind and “reflect” on them, thus constructing knowledge
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8. OBJECTS HAVE PRIMARY AND SECONDARY QUALITIES (p.253)
Primary qualities “resemble” (or “reside in”) an object even when we are not perceiving the object
Solidity
Extension
Figure (shape)
Motion or rest
Number
Secondary qualities do not “resemble” (or “reside in”) an object, but are “powers” of objects to produce sensations in our minds
Colors
Sounds
Tastes
Odors
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9. Locke’s “Substance”
What holds these primary and secondary qualities together to make them the same entity?
Locke: “Substance” (something that lies beneath these observable qualities).
But do we perceive any “substance”?--- empiricism finds its own difficulty.
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10. Empiricist turning into Idealist: GEORGE BERKELEY: “TO BE IS TO BE PERCEIVED”
There is no such thing as material substance; all that exist are “minds” and “ideas”
There is no distinction between “primary” and “secondary” qualities
What we mistakenly believe to be “material objects” are really collections of ideas in the mind of God
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11. The Fate of Empiricism
With the success of Newtonian physics and Locke’s account of an empiricist metaphysics and epistemology
Empiricism seemed to clearly have the upper hand against rationalism
David Hume ( ) comes along and shows that there is something deeply troubling about empiricism
It leads to a radical kind of skepticism
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12. Hume’s Version of Empiricism
Contents of the mind can be divided into two categories
Impressions-- the actual experiences that we have
Tasting an apple, seeing a sunset, feeling pain, or angry or jealous, hungry or sad, etc
Ideas– Copies of impressions
My memory of the taste of the apple, my idea of anger, jealousy, hunger, red
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13. Hume on Perception
Impressions and ideas are each a kind of perception for Hume
they are distinguished by their ‘force and vivacity’
Impressions are ‘our more lively perceptions’
Ideas (or thoughts) are dull and lifeless copies of the original impression
This means that both are merely mental phenomena
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14. The Empiricist Theory of Meaning
Words in language stand for ideas
Hume endorses Locke’s distinction between simple and complex ideas
Complex ideas are composed of simple ones
Simples ones either can be traced back to an impression from which they were copied
Or else they are meaningless nonsense
If an idea cannot be traced back to an impression it is meaningless and should not be used
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15. Empiricist Epistemology
Human knowledge falls into two kinds for Hume
Relations of Ideas– all rational a priori knowledge
Matters of Fact– all empirical a posterori knowledge
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16. Relations of Ideas & Matters of Fact
All bachelors are unmarried
All triangles have three sides
A2+B2=C2
(3 x 5)=(1/2 x 30)
For any sentence S, either S is true or S is false
S can’t be true and also not true at the same time
Matters of Fact
All bachelors are messy
All dogs have four legs
Apples are red
Rent in NYC is expensive
Subway fare is $2.00
Fire causes pain
Objects when dropped will fall
The future will resemble the past
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17. Hume’s Skepticism of External World
We can only experience our experience.
We do not know what is beyond our experience (“external world”).
“Mind” “Experience” “External World”
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18. Cause and Effect
All of our ideas must come from one of these two sources (matters of fact; relations of ideas)
One of the most important ideas we have is the idea of causation
The idea of a necessary connection between events
Same cause = same effect EVERY TIME
All of science is based on this idea. All of our common sense knowledge about the world is based on this idea. BUT we NEVER “see” CAUSATION, just the association of two things!
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19. It’s just a Habit! So where does the idea come from?
It comes from ‘a habit of expectation’
We see A happen
We see B happen right after
This is repeated
Soon when we see A happen we come to expect that B will happen right after
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20. Hume’s Challenge to Induction
Induction: The process of deriving general principles from particular facts or instances.
All inductive knowledge is based on the fallacy of assuming that the future will resemble the past
But just that something has happened for a long time is no guarantee that it will always happen
So, the sun may have risen everyday so far, but who can say with certainty that it will rise tomorrow?
Just like problem of black swans
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21. Pavlov & Classical Conditioning
We have been trained by nature to expect certain events upon seeing certain other events
Just like Pavlov’s dog
You ring the bell and bring some food
The dog salivates
Repeat
Soon the dog salivates when hearing the bell whether or not food comes
The dog has come to expect ‘bell then food’
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22. KANT’S “COPERNICAN REVOLUTION”: OVERCOMING SKEPTICISM BY UNITING EMPIRICISM AND RATIONALISM
“Hitherto it has been assumed that all our knowledge must conform to objects. But all attempts to extend our knowledge of objects by establishing something in regard to them by means of concepts have, on this assumption, ended in failure. We must, therefore, make trial whether we may have more success if we suppose that objects must conform to our knowledge.” –Critique of Pure Reason
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28. Kant’s Dogmatic Slumber
Kant is disturbed from thinking that everything in science is fine by Hume’s argument
Empiricism cannot deliver necessary truths
‘experience can teach us that something is the case but it cannot teach us that it must be the case’
Yet science claims to discover necessary truths about nature (Scientific necessity)
Even worse, Hume claimed to have shown that human beings are essentially irrational
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29. The Structure of Experience
How could our experience be the way that it is?
How is it?
Objects are located in space and time
Can you imagine an object which was not at any place?
No !
This is something that we can know a priori
It is not dependent on experience
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30. Conditions of all Possible Experience
It is the pre-condition for any experience at all
Just like space in the room is a precondition of having objects in the room
So too space is a necessary condition of any possible experience
Thus we can know with absolute certainty that whatever experiences we do have will all take place at some time and at some particular place
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31. The A Priori So Kant concludes that there is pure a priori knowledge
‘pure’ because it does not depend on experience
But is rather the pre-conditions for any possible experience
It is necessary
It is not possible to have experience without space
And universal
All experiences will be in space
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32. How does this analogy help?
In this analogy, raw sense data is like the bag of mixed coins. In itself, raw sense data is meaningless jumble.
The coin sorter is analogous to the mind’s categories.
The coin sorter provides organisation and structure and, thereby, value to the bag of coins.
The mind’s categories provide organisation and structure and, thereby, meaning, to jumbled up, raw sense data.
Write your own analogy…try the rules of chess and chess pieces, glasses for a short-sighted person, containers for things contained…

33. Synthetic A Priori Knowledge
So Kant’s answer to Hume is his theory of synthetic a priori knowledge
Take ‘fire causes pain’
It is synthetic, it adds to our experience
But it is also a priori, that is, necessary and universal
It is a priori in the sense that we can tell by looking at the structure of our experience that it must be a certain way
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34. Phenomena vs. Noumena
The phenomenal world is the world as it appears to us.
It is the world that we see, touch, taste, etc.
The noumenal world is the way that the world is in-itself
The world as it is by itself
All we can know is the way our experience of the world will be
We can’t know the noumenal world
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35. Phenomena v. Noumena II Wasup? Hi Noumena Sensibility Understanding
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36. Phenomena v. Noumena IIIHi
Wasup? Hi
Wasup? Me
You
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37. Kant’s Philosophy of Mind
Our minds are the same (i.e., we share the same phenomenal world)
The mind has two components
Sensibility
Understanding
“Sensibility” takes in ‘raw’ unorganized noumena and organizes it into phenomena (our experience)
Each has their categories that they use in order to construct our experience
The sensibility has Space and Time
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38. A descriptive analogy to help: The Coin Sorting Machine
Take a large bag of mixed coins of different types. Is there £200 there, or £25?
While they remain mixed up in the bag, the coins really have no value. You cannot buy something with a bag of coins without knowing its value.
Before you can spend the coins, you have to sort them with a coin sorter so that you know how much they are worth.
The coins don’t really have any true value until they are sorted by the coin sorter.

39. Kant’s Philosophy of Mind
That is the only way that experience like ours is possible
The same cause must bring about the same effect
Because our mind constructs the world that way.
Yet this comes at a heavy cost
Science studies our experience of the world
It does not, cannot, study the noumenal world
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40. Unity, plurality, totality Quality Reality, negation, limitation
Kant’s Categories
There are four main categories, each divided into three sub-categories. (HANDY TO KNOW THESE BY HEART…)
Quantity
Unity, plurality, totality
Quality
Reality, negation, limitation
Relation
Substance and accident, cause and effect, reciprocity
Modality
Possibility, existence, necessity

41. Kant’s Philosophy of Mind
Kant called this a Copernican Revolution in philosophy
Instead of the mind passively acting like a recorder of an outside reality
Kant sees the human mind as actively constructing reality
This is his mix of Rationalism and Empiricism
Empiricism– science is synthetic knowledge
Rationalism– but based on a priori categories
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42. KANT ON THE SYNTETIC A PRIORI AND THE PHENOMENAL AND NOUMENAL WORLDS
THE SYNTHETIC A PRIORI
THE PHENOMENAL AND NOUMENAL WORLDS
Necessary and universally true
a priori—can be discovered independently of experience
Synthetic in the sense that it provides us with genuine information regarding our experience in the world
phenomenal reality is the world as we constitute it and experience it
noumenal reality is the world beyond our perceptions, reality “in-itself”
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43. What is your epistemology?
Where does Scientific knowledge (e.g., “Normally water freezes below 0° C”) come from?
From experience (empiricism like Locke)
From reasoning (rationalism)
We do not have such knowledge (Hume)
We construct such knowledge in our mind with data from experience (Kant)
???
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