Explanation Slides

Prediction vs. ExplanationPrediction vs. Explanation

PHIL 160PHIL 160PHIL 160PHIL 160

What will happen next?

What will happen next?

Why did it happen?

Why did it happen?

Prediction:

Prediction:

Explanation:

Explanation:


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 have to happen?

How is it possible for

this to happen?Why did this happen

rather than something else?

Why did it happen?

Why did it happen?

Deductive-Nomological modelDeductive-Nomological model


• An explanation is a deductive argument.

• Conclusion = fact to be explained.

• Premises include a “law of nature” (universal regularity).

• An explanation is a deductive argument.

• Conclusion = fact to be explained.

• Premises include a “law of nature” (universal regularity).

(from “nomos”, Greek for “law”)

(from “nomos”, Greek for “law”)

Why is this bird black?Why is this bird black?


1. This bird is a raven.

2. All ravens are black.

1. This bird is a raven.

2. All ravens are black. This bird is

black. This bird is

black.

Deductive-Nomological modelDeductive-Nomological model


• 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”.

• 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”

at work in “intertheoretic

reduction”



Why does the pressure of this gas

sample increase?


sample increase?


1. The volume of the gas sample is decreased.

2. Boyle’s law: PV= k.

1. The volume of the gas sample is decreased.

2. Boyle’s law: PV= k.

The pressure of the gas sample increases.The pressure of the gas sample increases.


Kinetic Theory of Gases:

Kinetic Theory of Gases:A gas is a collection of

point particles:• occupying negligible volume.

• in constant motion through entire container.

A gas is a collection of point particles:

• occupying negligible volume.








• undergoing elastic collisions with walls of container and other particles.




• undergoing elastic collisions with walls of container and other particles.


“Bridge Laws”

“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.

Volume = space through which point particles are moving

Pressure = force from collisions with walls/area

Temperature = measure of the kinetic energy of the particles.



Volume of the gas sample

is decreased (less space for

particlesto move through).

Volume of the gas sample

is decreased (less space for

particlesto move through).


sample increase?


sample increase?


sample increase?


sample increase?


Same number of particles with same

kinetic energy

more frequent collisions with

walls.

Same number of particles with same

kinetic energy

more frequent collisions with

walls.


More frequent collisions with

walls

higher force/area

(i.e., higher pressure)

More frequent collisions with

walls

higher force/area

(i.e., higher pressure)


sample increase?


sample increase?

Does D-N model work for all explanations?

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?

• Is every argument that fits the model a good explanation?

• Does every good explanation fit the model?

PHIL 160PHIL 160PHIL 160PHIL 160 Alex didn’t get

pregnant. Alex didn’t get

pregnant.

Why didn’t Alex 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.

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.


Why did the salt dissolve?Why did the salt dissolve?


1. I hexed the salt.

2. I put the (hexed) salt in water.

3. Hexed salt dissolves in water.

1. I hexed the salt.

2. I put the (hexed) salt in water.

3. Hexed salt dissolves in water.

The salt dissolved. The salt dissolved.


1. I put the salt in water.

2. Salt dissolves in water.

1. I put the salt in water.

2. Salt dissolves in water. The salt

dissolved. The salt dissolved.Hexing is not explanatorily

relevant!

Hexing is not explanatorily

relevant!

Why did the salt dissolve?Why did the salt dissolve?

Why did Nancy get lung cancer?Why did Nancy get lung cancer?


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.

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. Nancy got lung

cancer.


Smoking 2 packs of cigarettes a day for 10 years causes lung cancer.

Smoking 2 packs of cigarettes a day for 10 years causes lung cancer.

Not for every smoker!

Not for every smoker!

Not a law of nature.

Not a law of nature.

Why did Nancy get lung cancer?Why did Nancy get lung cancer?


Why did these camellias die?Why did these camellias die?


1. The camellias were planted in hot, rich soil.

2. Hot soil damages camellia roots.


2. Hot soil damages camellia roots. These camellias

died. These camellias

died.

Why did these camellias thrive?Why did these camellias thrive?



2. Camellias grow well in rich soil.


2. Camellias grow well in rich soil. These camellias

thrived. These camellias

thrived.

Cartwright:We don’t need a law!

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.)

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.)


Why is the flagpole’s shadow

4 meters long?

Why is the flagpole’s shadow

4 meters long?


1. Flagpole is 3 m high.

2. Sunlight strikes pole at angle .

3. Shadow length = height of pole x tan .

1. Flagpole is 3 m high.


3. Shadow length = height of pole x tan . Shadow length =

4 m. Shadow length =

4 m.

Good deductive argument, BAD explanation!

Good deductive argument, BAD explanation!


1. Shadow length is 4 m.


3. Shadow length = height of pole x tan .

1. Shadow length is 4 m.


3. Shadow length = height of pole x tan . Height of pole =

3 m. Height of pole =

3 m.


What kind of explanations in

science?

What kind of explanations in

science?Looking for universal

regularities or statistical

regularities?

Looking for universal

regularities or statistical

regularities?Possible mechanisms or

how it actually happened?

(Causes, or something else?)

Possible mechanisms or how it actually

happened?(Causes, or something

else?)

Education

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