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Rationalist Epistemology. Plato Descartes (427-347 B.C.E. ) (1596-1650). Epistemology. Is the philosophical study of Knowledge. What is knowledge? What is the difference between knowledge and opinion? What is the origin of knowledge? Reason: Rationalism
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Rationalist Epistemology Plato Descartes (427-347 B.C.E.)(1596-1650)
Epistemology • Is the philosophical study of Knowledge. • What is knowledge? • What is the difference between knowledge and opinion? • What is the origin of knowledge? • Reason: Rationalism • Experience: Empiricism
How can we know something? • BelieveIn order for you to know X, you must believe X. • TruthIn order for you to know X, X must be true. • JustificationIn order for you to know X, you must be able to give a justification for your belief. • Gettier Problems.
A priori Knowledge:Known independent of experience. • Two parallel lines cut by transversal. Prove A=H. • A = D—Opposite angles are congruent. • D = H—Corresponding angles are congruent. • A = H—substitution. • What if we measure and they are not equal?
Simile of the Line __________________________________ Pure Reason The Forms __________________________________Understanding Scientific Concepts__________________________________Belief Sensible Objects__________________________________Imagining Images _________________________________
Ontology • ImagesShadows and reflections of objects. Objects are more real than shadows because they last longer and are not dependent on shadows. • Sensible ObjectsThey are not absolutely real because they do not last and they are dependent on other things, like the sun. • Conceptual LevelWe 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.
Ontology • ConceptsCapture the unchanging relations. Things can fall in many different ways; but the concept of gravity explains these events through one unchanging law. • FormsThe archetypes of everything existing in the visible universe. • Grasped by the intellect not the senses. • Move from the definition to the formula.
Meno’s Paradox • How will you try to find out something (knowledge), Socrates, when you have no notion at all what it is? • Innate IdeasIdeas 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. • MenoHe knew all along how to double the square, Socrates helped him remember.
Descartes and the Copernican Revolution Copernicus (1473-1543) • Geocentric ViewConsistent with religious view that humans are the purpose of creation. • Power of ReasonThe church and the Non-scientist made irrelevant. • The InquisitionArrested Galileo in 1632 for discovering the moons of Jupiter.
Descartes • Reconciling Reason and FaithScientific advances threaten the authority of the church. Descartes’ view reconciles reason and faith. • Uses reason and logic • To prove existence of God and Soul.
Descartes’ Method • RationalismTrue knowledge comes from reason. Thus it is a priori, known prior to experience. • Innate IdeasPlaced in our mind by God. (cp. to Plato’s forms) • Mathematical ModelFather of Trigonometry.
Descartes’ Method • Methodic DoubtIf 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 I think, therefore I am. • IndubitableKnown clearly and distinctly, even if God is an evil genius. • Immaterial SoulI know I exist as a thinking thing when I think. The soul is immaterial and can exist independent of the body.
Immaterial Soul • Cartesian 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.
God • Can’t Be Evil Genius Would not be perfect. • Senses and Reason Can therefore be trusted because they come from God. • External World Exists He’s out of his mind. • Our knowledge of self and God provide a foundation for all knowledge.