the nature of logic
TRANSCRIPT
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 14
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
philosophylandered u
Homepage gt Logic gt The Structure of Arguments gt The Nature of Logic
Quizzes
Tests
FAQ
Links
Search
Readings
Archives
Syllabus
Philosophy 103 Introduction to LogicThe Nature of Logic
Abstract Some of the uses of logic are illustrated and deductive arguments are brieflydistinguished from inductive arguments
I Logic is the study of the methods and principles used indistinguishing correct from incorrect reasoning
B Logic differs from psychology in being a normative or aprescriptive discipline rather than a descriptive discipline
1 Ie it prescribes how one ought to reason its not concernedwith how one actually does reason
2 Logic is concerned with laying down the rules for correctreasoning
3 Consequently logic seeks to distinguish good argumentsfrom poor ones
II How Logic helps reasoning
A Practice makes better Some examples of how this coursecan help reasoning about the world are as follows
1 Consider this syllogism
All followers of Senator Jones are in favor of higher taxesAll communists are in favor of higher taxesAll followers of Senator Jones are communists
It will become easy for us to recognize the fallacy in thisargument as the fallacy of the undistributed middle term
2 Consider this informal argument
In spite of the large number of UFO spottings that can beattributed to weather conditions and known aircraft and other factors there are hundreds of sightings that cannot beaccounted for Hence we can safely conclude that UFOs exit
Consider this counter-example
In spite of the large number of quarters put under kids
Arguments Language Fallacies Propositions Syllogisms Translation Symbolic Home
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 24
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
pillows which can be attributed to sneaky parents brotherssisters and so forth there are hundreds of cases which cannot
be accounted for Therefore the tooth fairy exits
B As well this course can help with the negative approachmdash that we avoid errors by being aware of them eg being aware of common formal and informal fallacies
1 Consider the passage Napoleon became a great emperor because he was so short In this short argument the fallacy of false cause (or non causa pro causa) occurs If this argumentwere good all or most short persons would become greatemperors
2 Consider the passage People in developing countries get oldas an earlier age because the average life expectancy is so shortin those countries Due to infant mortality people do not getolder more quickly the fallacy of division occurs
C Methods criteria and techniques all are given as methods of testing correctness These are some of the techniques we will belearning and using in this class These methods are shown heremerely for purposes of illustration
1 For example we can draw Venn Diagrams to show thefallacy of the undistributed middle term in problem I A
discussed above
2 Or we can show the fallacy in I A by appealing to specificrules
All P is M u
All S is M uAll S is P
The term shared by both premisses is said to be undistributed because it does not refer to each and every persons in favor of higher taxes
III There are several kinds of logic which exhibit a kind of familyrelation dialectic multivalued logic logic of commands fuzzylogic etc
IV In this course basically we will use just two kinds of logicdeductive and inductive
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 34
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
A Deductive Logic concerned with determining when anargument is valid (ie deals with conclusive inferences)
1 A deductive argument is one which claims that its conclusionfollows with necessity
2 If that claim is not met then the argument is said to be
invalid
3 Consider this example from Time magazine about theKennedy assassination
Since tests proved that it took at least 23 seconds to operatethe bolt on Oswalds rifle Oswald obviously could not havefired three times--hitting Kennedy twice and Conally once--in56 second or less
23The first load ned not be counted
23 verses 23
+ 23 + 23
69 sec 46 sec
The response by Frederick T Wehr SirhellipThis argumentwhich has appeared in many publications since theassassination is faulty and I am surprised that I havent seenit refuted before this Assuming that the bolt of Oswalds rifle
can in fact be operated in 23 seconds then Oswalddefinitely could fire 3 shots in less than 56 seconds for astop watch would be started when the first shot was fired thesecond shot would be fired when the stop watch read 23seconds and the third shot would be fired when the stopwatch read 46 seconds You have apparently overlooked thefact that in the time it takes to fire 3 shots it is onlynecessary to operate the bolt twice
B Inductive Logic is concerned with the correctness of inferences for which the evidence is not conclusive (ie probable
inferences)
1 Hence an inductive argument is one whose conclusion isclaimed to follow with probability
2 Consider the example from Mark Twains Notebook hellipat bottom I did not believe I had touched that man The law of probabilities decreed me guiltless of his blood for in all mysmall experience with guns I had never hit anything I had triedto hit and I knew I had done my best to hit him
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 44
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
3 Or consider extrapolation techniques used in stock market prediction eg the wedge formation
V What logic is not
A Logic is not the science of the laws of thought--in which case itwould be a descriptive science like psychology
1 Sometimes people can come to conclusions reliably without
being able to know or explain how the conclusion was reached Eg the so-called intuitive type of personality
2 Often people can come to the right conclusion for the wrongreasons Logic is the study of the modes of correct reasoning asshown in an interpersonal manner
B Logic is not really the science of reasoning either because thelogician is not interested in the psychological processes of reasoning
1 The logician is interested in the structure of arguments
2 People infer statements and statements entail other statements
3 We want to say that the entailment is there even thoughsomeone does not at this time understand it
Send corrections or suggestions to webmaster at philosophylandereduRead the disclaimer concerning this page
091509 2004-9 Licensed under GFDL
Argumen ts | Language | Fallacies | Propositions | Syllogisms | Translation | Symbolic
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 24
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
pillows which can be attributed to sneaky parents brotherssisters and so forth there are hundreds of cases which cannot
be accounted for Therefore the tooth fairy exits
B As well this course can help with the negative approachmdash that we avoid errors by being aware of them eg being aware of common formal and informal fallacies
1 Consider the passage Napoleon became a great emperor because he was so short In this short argument the fallacy of false cause (or non causa pro causa) occurs If this argumentwere good all or most short persons would become greatemperors
2 Consider the passage People in developing countries get oldas an earlier age because the average life expectancy is so shortin those countries Due to infant mortality people do not getolder more quickly the fallacy of division occurs
C Methods criteria and techniques all are given as methods of testing correctness These are some of the techniques we will belearning and using in this class These methods are shown heremerely for purposes of illustration
1 For example we can draw Venn Diagrams to show thefallacy of the undistributed middle term in problem I A
discussed above
2 Or we can show the fallacy in I A by appealing to specificrules
All P is M u
All S is M uAll S is P
The term shared by both premisses is said to be undistributed because it does not refer to each and every persons in favor of higher taxes
III There are several kinds of logic which exhibit a kind of familyrelation dialectic multivalued logic logic of commands fuzzylogic etc
IV In this course basically we will use just two kinds of logicdeductive and inductive
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 34
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
A Deductive Logic concerned with determining when anargument is valid (ie deals with conclusive inferences)
1 A deductive argument is one which claims that its conclusionfollows with necessity
2 If that claim is not met then the argument is said to be
invalid
3 Consider this example from Time magazine about theKennedy assassination
Since tests proved that it took at least 23 seconds to operatethe bolt on Oswalds rifle Oswald obviously could not havefired three times--hitting Kennedy twice and Conally once--in56 second or less
23The first load ned not be counted
23 verses 23
+ 23 + 23
69 sec 46 sec
The response by Frederick T Wehr SirhellipThis argumentwhich has appeared in many publications since theassassination is faulty and I am surprised that I havent seenit refuted before this Assuming that the bolt of Oswalds rifle
can in fact be operated in 23 seconds then Oswalddefinitely could fire 3 shots in less than 56 seconds for astop watch would be started when the first shot was fired thesecond shot would be fired when the stop watch read 23seconds and the third shot would be fired when the stopwatch read 46 seconds You have apparently overlooked thefact that in the time it takes to fire 3 shots it is onlynecessary to operate the bolt twice
B Inductive Logic is concerned with the correctness of inferences for which the evidence is not conclusive (ie probable
inferences)
1 Hence an inductive argument is one whose conclusion isclaimed to follow with probability
2 Consider the example from Mark Twains Notebook hellipat bottom I did not believe I had touched that man The law of probabilities decreed me guiltless of his blood for in all mysmall experience with guns I had never hit anything I had triedto hit and I knew I had done my best to hit him
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 44
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
3 Or consider extrapolation techniques used in stock market prediction eg the wedge formation
V What logic is not
A Logic is not the science of the laws of thought--in which case itwould be a descriptive science like psychology
1 Sometimes people can come to conclusions reliably without
being able to know or explain how the conclusion was reached Eg the so-called intuitive type of personality
2 Often people can come to the right conclusion for the wrongreasons Logic is the study of the modes of correct reasoning asshown in an interpersonal manner
B Logic is not really the science of reasoning either because thelogician is not interested in the psychological processes of reasoning
1 The logician is interested in the structure of arguments
2 People infer statements and statements entail other statements
3 We want to say that the entailment is there even thoughsomeone does not at this time understand it
Send corrections or suggestions to webmaster at philosophylandereduRead the disclaimer concerning this page
091509 2004-9 Licensed under GFDL
Argumen ts | Language | Fallacies | Propositions | Syllogisms | Translation | Symbolic
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 34
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
A Deductive Logic concerned with determining when anargument is valid (ie deals with conclusive inferences)
1 A deductive argument is one which claims that its conclusionfollows with necessity
2 If that claim is not met then the argument is said to be
invalid
3 Consider this example from Time magazine about theKennedy assassination
Since tests proved that it took at least 23 seconds to operatethe bolt on Oswalds rifle Oswald obviously could not havefired three times--hitting Kennedy twice and Conally once--in56 second or less
23The first load ned not be counted
23 verses 23
+ 23 + 23
69 sec 46 sec
The response by Frederick T Wehr SirhellipThis argumentwhich has appeared in many publications since theassassination is faulty and I am surprised that I havent seenit refuted before this Assuming that the bolt of Oswalds rifle
can in fact be operated in 23 seconds then Oswalddefinitely could fire 3 shots in less than 56 seconds for astop watch would be started when the first shot was fired thesecond shot would be fired when the stop watch read 23seconds and the third shot would be fired when the stopwatch read 46 seconds You have apparently overlooked thefact that in the time it takes to fire 3 shots it is onlynecessary to operate the bolt twice
B Inductive Logic is concerned with the correctness of inferences for which the evidence is not conclusive (ie probable
inferences)
1 Hence an inductive argument is one whose conclusion isclaimed to follow with probability
2 Consider the example from Mark Twains Notebook hellipat bottom I did not believe I had touched that man The law of probabilities decreed me guiltless of his blood for in all mysmall experience with guns I had never hit anything I had triedto hit and I knew I had done my best to hit him
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 44
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
3 Or consider extrapolation techniques used in stock market prediction eg the wedge formation
V What logic is not
A Logic is not the science of the laws of thought--in which case itwould be a descriptive science like psychology
1 Sometimes people can come to conclusions reliably without
being able to know or explain how the conclusion was reached Eg the so-called intuitive type of personality
2 Often people can come to the right conclusion for the wrongreasons Logic is the study of the modes of correct reasoning asshown in an interpersonal manner
B Logic is not really the science of reasoning either because thelogician is not interested in the psychological processes of reasoning
1 The logician is interested in the structure of arguments
2 People infer statements and statements entail other statements
3 We want to say that the entailment is there even thoughsomeone does not at this time understand it
Send corrections or suggestions to webmaster at philosophylandereduRead the disclaimer concerning this page
091509 2004-9 Licensed under GFDL
Argumen ts | Language | Fallacies | Propositions | Syllogisms | Translation | Symbolic
7242019 The Nature of Logic
httpslidepdfcomreaderfullthe-nature-of-logic 44
162016 The Nature of Logic
httpphilosophylanderedulogicnature_loghtml
3 Or consider extrapolation techniques used in stock market prediction eg the wedge formation
V What logic is not
A Logic is not the science of the laws of thought--in which case itwould be a descriptive science like psychology
1 Sometimes people can come to conclusions reliably without
being able to know or explain how the conclusion was reached Eg the so-called intuitive type of personality
2 Often people can come to the right conclusion for the wrongreasons Logic is the study of the modes of correct reasoning asshown in an interpersonal manner
B Logic is not really the science of reasoning either because thelogician is not interested in the psychological processes of reasoning
1 The logician is interested in the structure of arguments
2 People infer statements and statements entail other statements
3 We want to say that the entailment is there even thoughsomeone does not at this time understand it
Send corrections or suggestions to webmaster at philosophylandereduRead the disclaimer concerning this page
091509 2004-9 Licensed under GFDL
Argumen ts | Language | Fallacies | Propositions | Syllogisms | Translation | Symbolic