Phil 160 lecture, "Kuhn: Crisis and Revolution," San Jose State University.

1. PHIL 160 PHIL 160 "Kuhn: Crisis & Revolution"

2. PHIL 160 NORMAL SCIENCE CRISIS REVOLUTION

3. PHIL 160 LEARNING OBJECTIVES: PHIL 160 • Crisis (questioning the paradigm) • Factors for choosing between paradigms • Subjectivity of paradigm shift

4. PHIL 160 PARADIGM

5. PARADIGM • Ideas about what kind of stuff • Ideas about what kinds of behaviors PHIL 160

6. PARADIGM • Methodology • Interesting questions (puzzles) • What counts as a good explanation • Ideas about what kind of stuff • Ideas about what kinds of behaviors PHIL 160

7. Puzzle-solving PHIL 160 NORMAL SCIENCE Shared PARADIGM

8. PHIL 160 Puzzle-solving Solved puzzles NORMAL SCIENCE Shared PARADIGM

9. Resistant Puzzles PHIL 160 Puzzle-solving Solved puzzles NORMAL SCIENCE Shared PARADIGM

10. If paradigm is right, these puzzles have solutions … but we can’t find them! Resistant Puzzles PHIL 160 Puzzle-solving Solved puzzles ANOMALIES NORMAL SCIENCE Shared PARADIGM

11. PHIL 160 NORMAL SCIENCE Shared PARADIGM Puzzle-solving Solved puzzles CRISIS ANOMALIES Resistant Puzzles

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13. PHIL 160 CRISIS

14. PHIL 160 CRISIS • Proliferation of different adjustments to the paradigm • Erosion of agreement about fundamentals • Suspicion that paradigm is fatally flawed

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16. NORMAL SCIENCE CRISIS PHIL 160 shared assumptions different assumptions How to keep doing science?

22. PHIL 160 Phenomena to be explained: 1. Sun’s yearly movement against the background of the zodiac constellations (one full circuit/year). (Includes positions of sunrises and sunsets, positions of noontime sun on solstices and equinoces.) Utterly commonsense assumption: the Earth isn’t moving.

23. PHIL 160 Two-sphere model of the universe:

24. PHIL 160 Two-sphere model of the universe: whole celestial sphere rotates once per day.

25. PHIL 160 Two-sphere model of the universe: whole celestial sphere rotates once per day. Sun travels along ecliptic approx 1 o per day (full circuit once per year)

26. PHIL 160 Phenomena to be explained: 2. Planets’ movement against the background of fixed stars. (Different rates for different planets.) Very convenient fact: Each of the planets travels roughly along the belt of zodiac constellations (the ecliptic). Can use 2-dimensional model (the plane the ecliptic cuts through the celestial sphere)

27. PHIL 160 Basic model for planetary motion: Earth at center. (“Geocentric” system) Sun and planets orbiting Earth on circular orbits of various sizes.

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31. PHIL 160 Refinements to the model:

32. PHIL 160 Refinements to the model: Planets travel on little circles (epicycles) …

33. PHIL 160 Refinements to the model: Planets travel on little circles (epicycles) … … which go around Earth on deferent (big) circles)

34. PHIL 160 Refinements to the model: Planets travel on little circles (epicycles) … … which go around Earth on deferent (big) circles) Retrograde motion observed when planet is on inside of its epicycle.

35. PHIL 160 SUN C MARS EARTH

36. PHIL 160 How do epicycles help with inner planets? Inner planets stay within a certain maximum angular distance of the Sun. Important feature of Ptolemy’s model: Center of a planet’s epicycle stays lined up with the Sun on its orbit of the Earth.

37. PHIL 160 SUN EARTH VENUS C

38. PHIL 160 A pretty good model (with some anomalies) Explains retrograde motion of outer planets. Explains maximum angular distance of inner planets from Sun. But: Some portions of planets’ orbits are faster, others are slower. Planetary orbits are not perfectly circular.

39. PHIL 160 Make more modifications to fix anomalies? Shift Earth slightly from center of orbit. Eccentric model

40. PHIL 160 Make more modifications to fix anomalies? Equant model Shift planet’s center of motion from center of orbit P sweeps out equal angles in equal times. (Slower on top of circle, faster on bottom)

41. PHIL 160 EARTH MARS C

42. PHIL 160 Too much modification? What was a clean system is now pretty complicated. Hard to use to make predictions, calculations. (No longer strictly geocentric.) Unsolved puzzles: No explanation for sizes of epicycles and deferent circles. No explanation for why epicycles of inner planets orbit Earth at same rate as Sun and stay lined up with Sun.

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46. PHIL 160 Copernican (heliocentric) model: Put Sun at center of the system Earth and planets on circular orbits around the sun. Drop the epicycles!

47. PHIL 160 SUN C EARTH MARS

48. PHIL 160 Copernican model on retrograde:

49. PHIL 160 SUN EARTH VENUS

50. PHIL 160 Copernican (heliocentric) model: Copernicus explicitly argued that his system was geometrically equivalent to Ptolemy’s. (Predict the same planetary motions from a less complicated model.)

51. PHIL 160 SUN C MARS EARTH

52. PHIL 160 SUN C EARTH MARS

53. PHIL 160 SUN EARTH VENUS C

54. PHIL 160 SUN EARTH VENUS

55. PHIL 160 Beyond predictions of planetary motion: How do the Ptolemaic and Copernican paradigms fit with paradigms in nearby fields? Aristotelian Physics (grounded in 4-element theory of matter): “ Everything goes to its natural place.” Heavy elements (like water and earth) go toward center of universe, light elements away from center.

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60. PHIL 160 Beyond predictions of planetary motion: Christian theology: Earth at center of creation; Earth as unique (not just another planet).

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62. PHIL 160 Fit with observations: TIE (Make identical predictions) Ptolemy vs. Copernicus

63. Ptolemy vs. Copernicus PHIL 160 Solving/dissolving unsolved puzzles: COPERNICUS (Don’t have to explain alignment of epicycles if there are no epicycles)

65. PHIL 160 Aesthetics (simplicity): COPERNICUS (All those epicycles make things confusing) Ptolemy vs. Copernicus

66. PHIL 160 Split decision: who wins? (Which factors are most important for the choice?) Ptolemy vs. Copernicus

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70. PHIL 160 What we observe is paradigm dependent ! (So, how is a paradigm shift progress?) NEXT CLASS

71. PHIL 160 LEARNING OBJECTIVES: PHIL 160 • Crisis (questioning the paradigm) • Factors for choosing between paradigms • Subjectivity of paradigm shift PHIL 160 PHIL 160