How Do You Know What the Right Logic Is?fitelson.org/bridges2/priest.pdf · 2015. 9. 20. · Graham...

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How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

How Do You Know What the Right Logic Is?

Graham Priest

September 17, 2015

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Introduction

1 Some Crucial Distinctions

2 A Little History

3 A Model for Theory-Choice

4 Comments on the Model

5 A Problem for the Model?

6 Conclusion

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

1 Some Crucial Distinctions

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Pure and Applied

Geometry

Logic

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Pure and Applied

Geometry

Logic

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

2 A Little History

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Darapti

All As are BsAll As are C s

So:Some Bs are C s

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Explosion

No As are BsSome Bs are As

So:All As are As

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

3 A Model of Theory Choice

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Criteria of Goodness

adequacy to the data

simplicity

consistency

power

avoidance of ad hoc elements

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Formal Model; Components

Criteria: {c1, ..., cn}.Measuring scale: [−10,+10] ⊆ Z.Measure function: µc

for any theory, T , µc(T ) ∈ [−10,+10].

Weights: wc

for any criterion, c , wc ∈ [−10,+10].

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Formal Model. Definitions

Rationality index: ρ

ρ(T ) = wc1µc1(T ) + ...+ wcnµcn(T )

If the theories on the table are T1, ..., Tk , the rationallypreferable one is that with the highest rationality index.

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Formal Model. Definitions

Rationality index: ρ

ρ(T ) = wc1µc1(T ) + ...+ wcnµcn(T )

If the theories on the table are T1, ..., Tk , the rationallypreferable one is that with the highest rationality index.

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

An Example

From traditional logic to classical logic

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

4 Comments on the Model

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Comments

Rational reconstruction

Fallibilism

Situatedness

Data

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Comments

Rational reconstruction

Fallibilism

Situatedness

Data

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Comments

Rational reconstruction

Fallibilism

Situatedness

Data

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Comments

Rational reconstruction

Fallibilism

Situatedness

Data

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Data

John is in Rome.If John is in Rome he is in Italy.

John is in Italy.

John is either in Rome or in Florence.If John is in Rome he is in Italy.If John is in Florence he is in Italy.

John is in Italy.

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Intuitively Invalid Inferences

John is either in Rome or in Florence.John is in Rome.

If John is in Rome he is in Italy.John is not in Rome.John is not in Italy.

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Another Intuitively Valid Inference

Mary is taller than John.John is taller than Betty.

Mary is taller than Betty.

For all people, x , y , and z , if x is taller than y and y istaller than z , then x is taller than z .

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Another Intuitively Valid Inference

Mary is taller than John.John is taller than Betty.

Mary is taller than Betty.

For all people, x , y , and z , if x is taller than y and y istaller than z , then x is taller than z .

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

5 A Problem for the Model?

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Problem?

Logic is required to revise logic

How much logic?

What can go wrong?

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Problem?

Logic is required to revise logic

How much logic?

What can go wrong?

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

A Problem?

Logic is required to revise logic

How much logic?

What can go wrong?

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Conclusion

How do you know what the right epistemology oflogic is?

How Do YouKnow Whatthe RightLogic Is?

Graham Priest

Some CrucialDistinctions

A LittleHistory

A Model forTheory-Choice

Comments onthe Model

A Problem forthe Model?

Conclusion

Conclusion

How do you know what the right epistemology oflogic is?

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