EpistemologyRationalism vs Empiricism

Skepticism• Do we really know anything? How do we know

that we know this?

• Consider the following statements:• The sky is blue• The confederation of Canada took place in 1867

Three types of skepticism

• Common sense• Philosophical• Absolute

Name that skepticism• Steve tells his girlfriend he was out late studying with his

ex-girlfriend. She does not know if he is telling the truth• After the death of a loved one, you begin to doubt the

existence of God• Doug feels that traditional morality doesn’t matter and

proceeds to defy all authority figures• You read a pamphlet by the government seeking re-

election and you wonder if it is all true• While filling out a philosophy worksheet, you begin to

doubt whether the information is accurate or meaningful at all

• Am I sitting in my chair right now? Do I exist? Does anyone?

Pyrrho• Greek philosopher 260-270 BCE• Started a group of philosophers called ‘The

Skeptics”• He taught that nothing can be known.• Use theory of opposites to support claim• He doubted all knowledge that is derived from the

senses and maintained that reason is no help in discovering knowledge because it is based on unreliable knowledge derived from the senses.

Aenesidemus’ modes of doubt

• People’s feelings and perceptions differ• Physical and mental differences among people

make things appear different• Different senses give people different impressions

of things• People’s perceptions depend on their physical

and intellectual condition when something is perceived

Aenesidemus’ modes of doubt

• Things appear different at different distances and positions

• People do not perceive things directly. Everything is perceived through a medium (i.e. air)

• Variations in the quantity, colour, motion, and temperature of things make them appear different

Aenesidemus’ modes of doubt

• People perceive familiar and unfamiliar things in different ways

• What people call knowledge is based only on the relation of things to other things or to themselves. Knowledge does not tell people what a thing is in itself.

• People’s opinions and customs are different in different countries

Is Ignorance Bliss?• Doubting that you can know anything for

certain carries with it certain concerns:o 'can you trust anyone?‘o 'does he/she really love you?‘o 'do you exist?'

• Pyrrho & Sextus didn't wallow in their scepticism; instead, they argued that the resolution to not knowing anything for certain was Ataraxia - an ancient variation on the idea 'don't worry, be happy'.

• After all, what if the reality really was you as a brain in a jar?

• Would you want to know that or would you rather continue as a virtual entity within an ultimately satisfying existence?

Think About it:

Rationalism• True knowledge acquired through reason alone• Senses can deceive• Major contributors: Plato, Descartes, Chomsky

Plato• Two worlds: -Material world – visible, imperfect world-Forms – perfect, invisible, innate ideas

• World of the senses changes constantly (i.e. colour of sky, temperature of lake)

• Form exists separately, in the human mind in a perfect invisible universe

Plato• People embark on an intellectual journey that

moves in stages from:-Dreaming and imagining-to believing-to thinking-Knowing

Problems with classical rationalism

• Assumptions are made by all cultural groups, faiths, disciplines and political parties.

• Commonly held assumptions have been challenged historically

-Women and right to vote, slavery, Newtonian universe, marriage

Rene Descartes• 17th century philosopher• Used skepticism as a tool to discover difference

between believing and knowing• Started by doubting everything• Used deductive reasoning to come up with two

conclusions-In the process of trying to understand knowledge he was doubting-Therefore he must be a doubter

Cogito ergo sum

(I think, therefore I am)Rene Descartes

Plato vs Descartes

• Both questioned information provided by unreliable sensory information

• Plato believed in existence of external world

• Descartes denied the existence of external world

• Plato concerned with content of thought whereas Descartes focused on process of thinking

• If a tree falls in the forest with no one around does anybody hear it?

Noam Chompsky• Expert in the field of linguistics• Knowledge of language and structures hard-wired

in humans• 4 year old children can comprehend a variety of

sentence structures even though they are not able to produce that structure (e.g. “me go night-night vs. It’s time to go to bed)

• Deep structure vs. Simple structure (e.g. spelling, phonics, style, grammar)

Empiricism• Challenged the emphasis on reason, innate ideas

and unreliability of sensory experience as a source of knowledge

• Not only a Western idea. Wang Chong and Dharamakirti also wrote of knowledge as a result of experience.

Aristotle• Plato’s student• Immaterial essence is inseparable from matter• Essence of things are in themselves• Used inductive reasoning to come to develop

generalizations of particular observations• Abstract world of Plato’s forms based on world of

objects that are perceived by the senses.• Sense perception and inductive reasoning are the

foundations of Aristotle’s theory of knowledge.

Thomas Aquinas• 13th century Dominican monk• Rejected Plato’s theory of forms• Shared many of Aristotle’s ideas but operated

within Christian framework• Supported scientific inquiry which, in some ways,

challenged fixed ideas of the Church

John Locke• Mind is blank slate or tabula rasa at birth• An Essay concerning Human Understanding• Sensations are what we directly experience which

lead to impressions• Our minds contemplate these impressions leading

to reflections that give birth to ideas.• Ideas are simple or complex combinations of

reflections of simple sensations.• E.g.. “hot” = simple impression “hot”, “liquid”, “bitter”, “black” = coffee

John Locke• Objects have primary and secondary qualities• Primary qualities are objective and they convey

factse.g.. Height, weight

• Secondary qualities are rely on subjective personal judgments

e.g., colour, taste sound

David Hume• Refined Locke’s theory of impressions and ideas• Impressions are stronger than ideas• Disputed idea of causality – people embrace

causality because it helps them make sense of their reality

• Highly skeptical of anything that cannot be perceived by the senses

• Also challenged scientific knowledge based on observations that can be replicated.

Kant we all just get along?

Experience without theory is blind, but theory without experience is mere intellectual play.

Immanuel Kant

Immanuel Kant• 18th century German philosopher• Schooled in Descartes’ theories of reason but

developed own theory of knowledge after being influenced by Hume’s skepticism

• Both reason and senses can be sources of knowledge

• Divided knowledge into 2 categories:o A posteriorio A priori – concepts that are organizes and unifies a posteriori

knowledge into certain innate concepts

Immanuel Kant• Mind is programmed to see relations between

objects and other phenomena experienced through the senses

• “Unity of consciousness” – Humans ideas are unique to the individual (sensory knowledge and reason are unified within a person’s mind)

• Allowed philosophers to move beyond the dichotomous arguments of rationalism and empiricism to propose new theories of knowledge