Explanation Slides

Slides from my lectures on explanation in Phil 160 ("Philosophy of Science") at San Jose State University.

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

2. PHIL 160PHIL 160
Why did it have to happen?
How is it possible for
this to happen?
Why did this happen rather
than something else?
Why did it happen?

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

4. Why is this bird black?
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1. This bird is a raven.
2. All ravens are black.
\ This bird is
black.

5. Deductive-Nomological model
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• 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”.
at work in
“intertheoretic reduction”

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7. PHIL 160PHIL 160

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

9. PHIL 160PHIL 160
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:
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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.

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12. “Bridge Laws”
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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 160PHIL 160

14. PHIL 160PHIL 160
Volume of the gas sample
is decreased
(less space for particles
to move through).
Why does the pressure of
this gas sample increase?

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

16. PHIL 160PHIL 160
More frequent
collisions with walls

Þ higher force/area
(i.e., higher pressure)
Why does the pressure of
this gas sample increase?

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

18. PHIL 160PHIL 160
\ Alex didn’t get pregnant.
Why didn’t Alex get pregnant?
1. Alex takes birth control
pills daily according to
the instructions.
2. Taken according to
instructions, birth control
pills are 99.9% effective
at preventing pregnancy.

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20. Why did the salt dissolve?
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1. I hexed the salt.
2. I put the (hexed) salt
in water.
3. Hexed salt dissolves
in water.
\ The salt dissolved.

21. PHIL 160PHIL 160
1. I put the salt in water.
2. Salt dissolves in water.
\ The salt dissolved.
Hexing is not
explanatorily relevant!
Why did the salt dissolve?

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

23. PHIL 160PHIL 160
Smoking 2 packs of
cigarettes a day for 10
years causes lung cancer.
Not for every smoker!
Not a law of nature.
Why did Nancy get lung cancer?

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25. Why did these camellias die?
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1. The camellias were
planted in hot, rich soil.
2. Hot soil damages camellia
roots.
\ These camellias died.

26. Why did these camellias thrive?
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1. The camellias were
planted in hot, rich soil.
2. Camellias grow well in
rich soil.
\ These camellias thrived.

27. Cartwright:
We don’t need a law!
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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.)

28. PHIL 160PHIL 160

29. Why is the flagpole’s shadow
4 meters long?
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1. Flagpole is 3 m high.
2. Sunlight strikes pole at
angle Q.
3. Shadow length =
height of pole x tan Q.
\ Shadow length = 4 m.

30. Good deductive argument,
BAD explanation!
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1. Shadow length is 4 m.
2. Sunlight strikes pole
at angle Q.
3. Shadow length =
height of pole x tan Q.
\ Height of pole = 3 m.

31. PHIL 160PHIL 160
What kind of explanations
in science?
Looking for universal
regularities or statistical
regularities?
Possible mechanisms or how
it actually happened?
(Causes, or something else?)