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Prediction vs. Explanation

Prediction vs. Explanation. Prediction:. What will happen next?. Explanation:. Why did it happen?. Why did it happen?. Why did it have to happen? How is it possible for this to happen? Why did this happen rather than something else?. Deductive- Nomological model.

christopherbryant
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Prediction vs. Explanation

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  1. Prediction vs. Explanation Prediction: What will happen next? Explanation: Why did it happen?

  2. Why did it happen? Why did it haveto happen? How is it possible for this to happen? Why did this happen rather than something else?

  3. Deductive-Nomological model (from “nomos”, Greek for “law”) • An explanation is a deductive argument. • Conclusion = fact to be explained. • Premises include a “law of nature” (universal regularity).

  4. Why is this bird black? This bird is a raven. All ravens are black.  This bird is black.

  5. Deductive-Nomological model at work in “intertheoretic reduction” • Reduce explanations from one theory to equivalent explanations in terms of another theory. • Explanation shed light on what’s really happening. • Often requires “bridge laws”.

  6. PHIL 160

  7. PHIL 160

  8. Why does the pressure of this gas sample increase? The volume of the gas sample is decreased. 2. Boyle’s law: PV= k. The pressure of the gas sample increases.

  9. Kinetic Theory of Gases: A gas is a collection of point particles: • occupying negligible volume. • in constant motion through entire container.

  10. Kinetic Theory of Gases: A gas is a collection of point particles: • occupying negligible volume. • in constant motion through entire container. • undergoing elastic collisions with walls of container and other particles.

  11. PHIL 160

  12. “Bridge Laws” Volume = space through which point particles are moving Pressure = force from collisions with walls/area Temperature = measure of the kinetic energy of the particles.

  13. PHIL 160

  14. Why does the pressure of this gas sample increase? Volume of the gas sample is decreased (less space for particlesto move through).

  15. Why does the pressure of this gas sample increase? Same number of particles with same kinetic energy  more frequent collisions with walls.

  16. Why does the pressure of this gas sample increase? More frequent collisions with walls  higher force/area (i.e., higher pressure) PHIL 160

  17. Does D-N model work for all explanations? • Is every argument that fits the model a good explanation? • Does every good explanation fit the model?

  18. Why didn’t Alex get pregnant? Alex takes birth control pills daily according to the instructions. Taken according to instructions, birth control pills are 99.9% effective at preventing pregnancy.  Alex didn’t get pregnant.

  19. Why did the salt dissolve? I hexed the salt. I put the (hexed) salt in water. Hexed salt dissolves in water.  The salt dissolved.

  20. Why did the salt dissolve? I put the salt in water. Salt dissolves in water.  The salt dissolved. Hexing is not explanatorily relevant!

  21. Why did Nancy get lung cancer? Nancy has smoked 2 packs of cigarettes a day for 10 years. Smoking 2 packs of cigarettes a day for 10 years causes lung cancer.  Nancy got lung cancer.

  22. Why did Nancy get lung cancer? Smoking 2 packs of cigarettes a day for 10 years causes lung cancer. Not for every smoker! Not a law of nature.

  23. Why did these camellias die? The camellias were planted in hot, rich soil. Hot soil damages camellia roots.  These camellias died.

  24. Why did these camellias thrive? The camellias were planted in hot, rich soil. Camellias grow well in rich soil.  These camellias thrived.

  25. Cartwright: We don’t need a law! We don’t need to know a law of nature to explain the camellias dying or thriving. There might be no such law of nature! (Explanation is still good.)

  26. Why is the flagpole’s shadow 4 meters long? Flagpole is 3 m high. Sunlight strikes pole at angle . Shadow length = height of pole x tan .  Shadow length = 4 m.

  27. Good deductive argument, BAD explanation! Shadow length is 4 m. Sunlight strikes pole at angle . Shadow length = height of pole x tan .  Height of pole = 3 m.

  28. What kind of explanations in science? Looking for universal regularities or statistical regularities? Possible mechanisms or how it actually happened? (Causes, or something else?)

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