1. Jewish, Christian, and Islamic Theories of Knowledge

2. Skepticism Beliefs (in a certain area) are –Unjustified (target: internalism) –Unreliable (target: externalism) So, (a certain kind of) knowledge is impossible Extreme form: all beliefs are unjustified or unreliable; all knowledge is impossible

3. Academic Skepticism Socrates: “All I know is that I know nothing.” Self-refuting? If you know nothing, how can you know that? Perhaps this can be solved: “I know only this.” But how do you know it? If you infer it, you must know that it follows from something else you know

4. Thesis and Recommendation “I know only this.” So what? Academic skeptics make recommendations Thesis: Knowledge (of a certain kind) is impossible Recommendation: So, one ought to _____. Problem: How can the extreme skeptic get from the thesis to the recommendation? –It seems that it requires an inference –But the skeptic can’t know that it follows

5. Pyrrhonian Skepticism “I don’t know anything—not even whether I know anything.” The Pyrrhonian skeptic –argues, but denies knowing whether skepticism follows from the premises –Makes no recommendations

6. Skepticism v. Relativism Relativism: There are no universally valid truths about the world Beliefs are true only relative to a –society –culture –historical epoch –interpretative community –individual person

7. Skepticism v. Relativism Knowledge of truth is impossible, because… –Skepticism: our beliefs are unjustified or unreliable –Relativism: there is no truth to know Protagoras: “Man is the measure of all things.”

8. Skepticism v. Relativism These might be seen as allies: –Skepticism is sometimes used as an argument for relativism: –If we can’t know truth, why think there’s any truth to know? (But note the inference problem) Or as enemies: –Skeptics stress the distance between appearance and reality –Relativists tend to bring them closer

9. Arguments for Skepticism

10. Philo of Alexandria (20 BCE-40) First to attempt project of reconciling Jewish scriptures with Greek philosophy Tries to construct skeptical arguments without metaphysical presuppositions in “On Drunkenness”

11. Argument from Variability Variability: Things are perceived differently by different beings at different times Undecidability: There is no neutral way to determine which perceptions are trustworthy Skeptical thesis: Therefore, knowledge is impossible

12. Variability Variation in perception among different species, different people, even same person on different occasions How do we know which portray reality accurately?

13. Argument from Illusion We often misperceive things There is no way to tell when we’re misperceiving things So, on any given occasion, we might be misperceiving things

14. Argument from Illusion Descartes: “To be sure, whatever I have so far admitted as most true I have learned either from the senses or through the senses. But sometimes I have caught them deceiving me, and it is prudent never to trust fully anything that has once deceived us.”

15. Illusion

22. Ambiguity

24. Misperception

26. Inattention We’re capable of missing a great deal if we’re paying attention to something else http://viscog.beckman.uiuc.edu/djs_lab/demo s.htmlhttp://viscog.beckman.uiuc.edu/djs_lab/demo s.html

27. Argument from Comparison We know, not things in themselves, but things in relation to other things— including us We know things only as they relate to us We can’t distinguish what’s really in the object from what we are contributing

28. Augustine (354-430) Logical and mathematical truths can be known, even if skeptical arguments succeed “I am certain that either there is only one world or there are more worlds than one. I am likewise certain that if there are more worlds than one, their number is either finite or infinite.”

29. Augustine: Perception “In fact, I believe that the senses are not untrustworthy either because deranged persons suffer illusions, or because we see things wrongly when we are asleep. If the senses correctly intimate things to the vigilant and the sane, it is no affair of theirs what the mind of a sleeping or insane person may fancy for itself.”

30. Augustine: Appearances “Restrict your assent to the mere fact of your being convinced that it appears thus to you. Then there is no deception, for I do not see how even an Academic [Skeptic] can refute a man who says: ‘I know that this appears white to me. I know that I am delighted by what I am hearing. I know that this smells pleasant to me. I know that this tastes sweet to me. I know that this feels cold to me.’”

31. Self-Knowledge “I am most certain that I am, and that I know and delight in this. In respect of these truths, I am not at all afraid of the arguments of the Academicians, who say, What if you are deceived? For if I am deceived, I am.... [C]ertainly I am not deceived in this knowledge that I am. And, consequently, neither am I deceived in knowing that I know. For, as I know that I am, so I know this also, that I know.”

32. An Epistemological Distinction Avicenna (ibn Sina, 980-1037): “Cognition can again be analyzed into two kinds. One is the kind that may be known through Intellect; it is known necessarily by reasoning through itself.... The other kind of cognition is one that is known by intuition [experience]. Whatever is known by Intellect... should be based on something which is known prior to the thing [that is, a priori].”

33. A Priori/A Posteriori Judgments A posteriori: dependent on experience; can be known only by experience A priori: independent of experience; can be known by reasoning alone

34. A Priori/A Posteriori A Posteriori: Hume, matters of fact: dependent on experience A Priori: Hume, relations of ideas: can be known “by mere operation of thought”

35. Concepts and Judgments Avicenna distinguishes knowledge of concepts from knowledge of judgments Rationalists and empiricists can disagree about both So, there are concept forms and judgment forms of each

36. First Principles? Avicenna –The whole is greater than its parts –Things equal to the same thing are equal to each other Descartes –I think, therefore I am –Anyone who thinks must exist while he/she thinks –Nothing is made from nothing –It’s impossible for anything to be and not be at the same time –What’s been done can’t be undone

37. The Flying Man Imagine a flying man, who is in a condition of sensory deprivation and has been his entire life No information arrives from any of the five senses Is there anything he could know? Is there anything of which he could be aware? Yes. He could be aware of his own existence and of his own awareness