rationalist epistemology plato descartes (427-347 b.c.e. )(1596-1650) plato descartes (427-347...

Download Rationalist Epistemology Plato Descartes (427-347 B.C.E. )(1596-1650) Plato Descartes (427-347 B.C.E. )(1596-1650)

Post on 03-Jan-2016




1 download

Embed Size (px)


  • Rationalist Epistemology Plato Descartes (427-347 B.C.E.)(1596-1650)

  • EpistemologyIs the philosophical study of Knowledge.What is knowledge?What is the difference between knowledge and opinion? What is the origin of knowledge?Reason: RationalismExperience: Empiricism

  • How can we know something?Believe In order for you to know X, you must believe X.Truth In order for you to know X, X must be true.Justification In order for you to know X, you must be able to give a justification for your belief.Gettier Problems.

  • Simile of the Line__________________________________Pure Reason The Forms __________________________________ Understanding Scientific Concepts __________________________________ Belief Sensible Objects __________________________________ Imagining Images_________________________________

  • OntologyImages Shadows and reflections of objects. Objects are more real than shadows because they last longer and are not dependent on shadows.Sensible Objects They are not absolutely real because they do not last and they are dependent on other things, like the sun.Conceptual Level We can know or understand sensible objects only by grasping them at the conceptual level. You must know and apply the definition of a horse to know you see one.

  • OntologyConcepts Capture the unchanging relations. Things can fall in many different ways; but the concept of gravity explains these events through one unchanging law.Forms The archetypes of everything existing in the visible universe. Grasped by the intellect not the senses. Move from the definition to the formula.

  • A priori Knowledge:Known independent of experience.Two parallel lines cut by transversal. Prove A=H. A = DOpposite angles are congruent.D = HCorresponding angles are congruent.A = Hsubstitution. What if we measure and they are not equal?

  • Menos ParadoxHow will you try to find out something (knowledge), Socrates, when you have no notion at all what it is?Innate Ideas Ideas present in the soul of the individual from birth. There is nothing the soul has not already learned. Learning is really remembering what we already know. Meno He knew all along how to double the square, Socrates helped him remember.

  • Descartes and the Copernican Revolution

    Geocentric View Consistent with religious view that humans are the purpose of creation.Power of Reason The church and the Non-scientist made irrelevant.The Inquisition Arrested Galileo in 1632 for discovering the moons of Jupiter. Copernicus (1473-1543)

  • Descartes Reconciling Reason and Faith Scientific advances threaten the authority of the church. Descartes view reconciles reason and faith.Uses reason and logicTo prove existence of God and Soul.

  • Descartes Method Rationalism True knowledge comes from reason. Thus it is a priori, known prior to experience.Innate Ideas Placed in our mind by God. (cp. to Platos forms)Mathematical Model Father of Trigonometry.

  • Descartes Method

    Methodic Doubt If you are not sure, consider it false. Need to begin fresh with truthful propositions.Am I Dreaming? The senses cannot be trusted.Evil Genius: brain in a vat, or matrix.Clear and Distinct Standard of truth. Understand the deduction.Standard Subjective?

  • Cogito, Ergo Sum

    Indubitable Known clearly and distinctly, even if God is an evil genius.Immaterial Soul I know I exist as a thinking thing when I think. The soul is immaterial and can exist independent of the body. I think, therefore I am.

  • Immaterial SoulCartesian Dualism Mind and body separate realms that interact through pineal gland. Independent but form whole.Mind/Body Problem How does something immaterial affect our material body?

  • God Solipsism All we can know is our own mind. God needed for Descartes to get out of his mind.Ontological Argument My idea of God is perfect; this idea must come from something as perfect that exists; God must exist.

  • GodCant Be Evil Genius Would not be perfect.Senses and Reason Can therefore be trusted because they come from God.External World Exists Hes out of his mind.Our knowledge of self and God provide a foundation for all knowledge.

  • Epistemology: the study of the nature, source, limits, & justification of knowledgeRationalism: we truly know only that of which we are certain. Since sense experience cannot guarantee certainty, reason alone must be the means for getting knowledgeReal knowledge about ourselves and the world is a priori (prior to and independent of experience). Knowledge gained from sense experience (a posteriori) is guaranteed only by appeal to reason

  • Rationalism: Sense Experience Does Not Provide KnowledgeDescartes: sense experiences are often wrong; I might be wrong about whether I have a body or if there is a world apart from my imagination (it may be a dream), and even whether my reasoning abilities (e.g., 2+3=5) can be trusted (evil genie)Shankara: we correct our experiences of self and world (e.g., hallucinations, sense perceptions) by knowing the oneness of ultimate reality (Brahman) (788-822)

  • Objections to Descartes Method of DoubtEven if some sense experiences are mistaken, that is no reason to doubt (even hypothetically) all of themLimiting knowledge only to what we know with certainty is too restrictive: we often know things a posteriori (i.e., based on experience), not on indubitable foundationsIf we doubt everything, we must also doubt whether we are truly doubtingwhich requires us to assume the existence of a public world of language users

  • Descartes Escape from DoubtI cannot doubt that I am doubting (thinking). All other knowledge is based on the undoubtable foundation that I exist: I think, therefore I exist (cogito ergo sum)I know I exist imperfectly only by first knowing perfect existence (God); and as a perfect being, God would not deceive me or allow me to be deceived when I know something (e.g., wax) clearly and distinctlythat is, as an intelligible (e.g., mathematical) object

  • Innate Ideas: knowledge of ideas or principles is possible only if they are inbornPlato: our knowledge of certain propositions is based on remembering truths acquired before our birthLeibniz: our recognition of ideas and truths is based on innate dispositions of the mindJainism: past unethical behavior blinds us to our innate knowledge of all things

  • EmpiricismAll knowledge of things in the world is a posteriori (that is, based ultimately on experience).Purely mental (i.e., a priori) operations of reason do not provide knowledge about the world.

  • John Locke (1632-1704):Representational Realism $ The mind at birth is a blank slate (tabula rasa): no ideas are innateKnowledge is based on experience of simple ideas (e.g., yellow) or complex ideas (lemon), relations (father), abstractions (humanity)We know about the world because our ideas of primary qualities (e.g., solidity, shape) represent things as they really are. Ideas of secondary qualities (e.g., colors) represent things only as they appear to us. Qualities are supported by (unknown) substances

  • George Berkeley (1685-1753)Primary qualities depend on the mind just as much as secondary qualitiesThere is no way to show how primary qualities represent real external qualities or substancesWhat we perceive is the real world, but the only things we perceive are our ideas. So the real world consists only of ideas and the minds that perceive them (including God). That is, the worlds existence consists in its being perceived (esse est percipi) in regular patterns

  • David Hume: Skepticism All knowledge of the world is a posterioribased on and limited to sense impressions or copies of those impressions or creations of imagination (ideas)We have no impressions of self or causality (other than temporal priority & continguity, but no necessary connection)only habitNotions of cause-effect and self are based on custom and natural inclination, not knowledge1711-1776

  • The Empiricists on CauseLocke: powers in material objects cause our ideas; ideas of primary qualities represent external thingsBerkeley: the concept of material objects outside our ideas is unintelligible; God causes our ideasHume: because the concept of cause is a relation of our ideas, a cause of our ideas is unintelligible GodExternal material bodiesIdeas in our mindcause is merely a habit of mind

  • Immanuel Kant (1724-1804)Rationalism is wrong: we are not born with innate ideas (e.g., equality, God, shortest distance is a straight line, future events will always have causes); we know things about the world only through perceptionsEmpiricism is wrong: sense data alone do not give us knowledge of the world. We can know only if our minds are not blank slates or passive receptacles of neutral sense data

  • Kants Epistemology: Transcendental IdealismWe know about things in the world not as they are in themselves (as noumena) but only insofar as they appear to us (as phenomena), universally structured by the minds categories (e.g., space, time, cause)Objections: (1) If we are limited to phenomena, we cannot know whether the world is really as it appears; (2) categories differ culturally and linguistically (SapirWhorf hypothesis)

  • Principles of Scientific KnowledgeUsing inductive reasoning and preferring the simplest generalizations, we c


View more >