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PHIL 101 DAY 3 Epistemology Day 2 Maymester 2007 The Traditional Definition of Knowledge Knowledge is: Justified True Belief When I believe that P P is true And I have the proper kind of reason to believe P (a Justification), Then, I Know P Skepticism Despite the fact that we ordinarily claim to have knowledge. Many people deny that knowledge is possible. The people are called “SKEPTICS” This is a key issue in Descartes Mediation I (see link on schedule) Skepticism (1) • Skepticism is the belief that knowledge is not possible, either in general or for some specific area or subject matter • Why would anyone deny the possibility of knowledge? (Is this just a wacky problem that philosophers have?) Skepticism (2) Classical Skepticism: Usually starts from disagreement or difference… A gap between appearance and reality Different perceptions of the same object Examples for Classical Skepticism 1. Sea Water –Poisonous to man, healthy for fish 2. Is the water hot? (after being in the cold, after being in the sun?) 3. Is 5’ 11” Larry Tall? Next to 6’ 4” Sam? Next to 4’ 3” Jerry? 4. Is the table flat? – how fine grained do you want to be? Skepticism (3) • Skepticism about Justification More modern forms of skepticism generally take the form of an attack on the possibility that a belief or beliefs can be justified Skepticism (4) Justification Skepticism a) Assumes a theory of justification b) Shows how common knowledge/beliefs will fail to be justified on that theory Can be Global or Local Universal Belief Falsifiers are Possible Skepticism (5) • Descartes (Hyperbolic Doubt) (Reading: Http://www.earlymoderntexts.com/pdfbits/dm1.pdf ) Principle of Hyperbolic Doubt “If I can doubt B, then I will assume that B is false” Yields certain knowledge. But knowledge is hard or impossible to get! An Ideal Knowledge test: Possible Beliefs Of all possible beliefs only those we know get called knowledge TEST The Hyperbolic Doubt Test All Possible Beliefs Doubt Test Beliefs you cannot doubt Beliefs it is possible to doubt Hyperbolic Doubt: Pro vs. Con PRO 1. Ensures certain knowledge 2. Eliminates all false beliefs 3. Test is easy to perform CON 1. Limits knowledge to certain truths 2. May eliminate some truths 3. Test is too demanding Does HYPERBOLIC DOUBT draw the line too narrowly? How does Cartesian Skepticim work? • The key moves all involve finding some basis upon which to doubt a belief or certain kinds of beliefs. Useful analogy: The Matrix movies “ARE YOU IN THE MATRIX RIGHT NOW?” Skepticism (6) Descartes’ Main Arguments: • Fallibility of the senses - Objects from a distance - Jaundice • The Argument from Dreams/Illusions • The Power of God - needs to be supplemented • The Evil Demon Skepticism (7) • Responses to Cartesian Skepticism 1) Accept Global Skepticism 2) Accept Hyperbolic Doubt and Look for Indubitable Knowledge (e.g. the Cogito) 3) Change our conception of justification. (Is Hyperbolic doubt our standard of justification?) Transition: If we give up Hyperbolic Doubt we risk the possibility that false beliefs might get treated as knowledge. Can we give up Hyperbolic Doubt unless we have an alternative test in mind? What test should we use? (…Partially Depends on what kinds of knowledge we accept) 2 Types of Knowledge • A Priori – Knowledge which does not require experience • A Posteriori – Knowledge that requires experience Ask: 1) Is there really an A Priori Knowledge? 2) Is there anything that cannot be known by experience alone? A Priori Knowledge? Here are some types of knowledge that people have claimed require a priori knowledge • • • • • Mathematical Truths Concept of God Concept of Infinity Concept of Immortality Linguistic Meanings Empiricism Many people think that knowledge is rooted in sense experience How much can we know by means of our senses? READ: Empiricism Section in Rauhut HUME: Enquiry Sections 1-5, esp. 2-3 (http://www.earlymoderntexts.com/pdfbits/he1.pdf) Empiricism (2) Definition of Empiricism: Empiricism is the view that our knowledge of the world is obtained primarily through our senses. Historically, this view is closely associated with the three British Empiricists: • John Locke • Bishop Berkley • David Hume Empiricism 3 What can we discover with our senses? 1. Basic sensory information (sense data) 2. If we have memory, then we can also discover which experiences are common or uncommon, which tend to go together, and which tend to precede or follow others. Empiricism 4 David Hume We will focus on the last of the British Empiricists, David Hume. According to Hume, the basic unit of empirical information is the IMPRESSION Empiricism 5 Hume’s Picture of “The Understanding” ALL PERCEPTIONS IDEAS Copies of Impressions Less Vivid Influenced by thought and memory IMPRESSIONS most vivid Strongest Empiricism 6 “Nothing in the Mind that was not first in the senses” Every perception (thought) is either a) an Impression b) b) an idea. Experience is complex, but we can abstract simple impressions from it. Empiricism 7 ABSTRACTION is the power of the understanding that allows us to pull out the experience of RED from the impression of the Apple. IMAGINATION allows us to combine simple ideas into complex ideas Empiricism 8 Once an impression is perceived it is immediately experienced, but if we reflect upon the impression or make it an object of thought, it becomes an idea. We have many ideas but they have only a few relations Empiricism 9 Relations of Ideas Resemblance (Is the experience similar to another?) Contiguity (Does the experience tend to come with another experience?) Cause and Effect (Conjunction-Does one experience always come after another) Empiricism 10 HUME’S FORK Hume allows that we can know: a) Matters of fact ( Complex immediate experiences – impressions) b) Relations of Ideas (How our ideas are related) The LIMITS of Humean Empiricism (1) We can have knowledge according to HUME, but it is limited. Hume’s theory of justification is roughly this: You are justified in believing that P just in case your belief that P resulted from an immediate impression or reflection upon the relations of ideas. The LIMITS of Humean Empiricism (2) We cannot know: 1) That we are identical with ourselves in the past 2) That one event causes another (needs explanation) 3) That God exists 4) That the future will be like the past. (Problem of induction – uniformity of nature assumption) 5) Cannot know laws of nature Hume the Skeptic? Ironically, Hume purchases knowledge at the price of forcing us to become skeptics about many things One option: Berkeley’s Idealism (Esse est Percipi) Solisipsm Mathematical Truths, Infinity, etc. Earlier I suggested that Empiricists need to tell a story about these concepts: Here it is: All of these are complex relations of ideas created by means of imagination e.g. Limit + negation = Infinity Is this story good enough?