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Patterns of Informal Non-Deductive Logic (Ch. 6)
Causal Reasoning
Chapter 6
1
Causal Reasoning
Causal reasoning establishes that one event caused another eventThere are lots of events that happen at the same time. Causal reasoning is made to identify specific events as causesand rule out coincidental events that happenat the same time.How did we get this flat tire? How come I have high blood pressure?What caused global warming?Event 1: Man-madeproduction of green house gasesEvent 2: Naturallyoccurring changes in atmosphereWhy did the dinosaurs die out?Event 1: Volcaniceruptions around the time of dinosaurs extinctionEvant2: Meteorhit the earth around the time of dinosaurs extinction
Requirements for a Good Causal Argument
Causal reasoning works when we know the events that happened and we want to know which event caused anotherEvents have to be insame time and spaceThecauseevent has to happenbeforetheeffecteventThe cause event and the effect event have to happen regularly
Three Fallacies of Causal Reasoning
The Post Hoc Fallacy: cause event happened before effect event but does not occur regularlyI whistled a tune, so my headache went awayMere Correlation Fallacy: cause event happened before effect and occurs regularly but is not the cause --- it’s a merely correlated eventEvery morning I wake up the sun rises. So, my waking up causes the sun to riseOversimplified Cause: cause event happened before effect, it occurs regularly with effect, but there is more than one causeUsing computers often happens before people become obese.Many people who use computers regularly become obeseSo, computer technology is the cause of obesity.
Abductive Reasoning
Chapter 6
2
Abductive Reasoning
Best Explanation ArgumentFact: Garage door open and bicycle missing from garage.Hypothesis 1: someone stole the bicycleHypothesis 2: my neighbors all conspired to steal the bicycleHypothesis 3: family member is out cyclingHypothesis 4: I forgot to close the garage door last night and left bicycle outsideHypothesis 5: alien took the bicycleNoteCannot collective inductive evidence (to make an inductive generalization)Do not have statistics to make a statistical argumentWe have not observed events that led to bicycle missing, so cannot make causal argument
Abductive Reasoning
Tim andTara haverecently had a terriblefight thatended their friendship. Now someone tells you that she just saw Tim andTara joggingtogether. The best explanation for this that you can think of is that they made up.
Abductive Reasoning
One morning you enter the kitchen to find a plate and cup on the table, with breadcrumbs and a pat of butter on it, and surrounded by a jar of jam, a pack of sugar, and an empty carton of milk. You conclude that one of your house-mates got up at night to make him- or herself a midnight snack and was too tired to clear the table.
Abductive Reasoning
Reasoning in Court and Circumstantial EvidenceOJ Simpson TrialOJ ran away from policeOJ was not in LA when NB & DG were murderedThe glove found at scene does not fit OJOJ was abusive to NBBlood type at scene matched OJ (about 0.5% ofpopulation)The detective involved with case wasracistSo,OJ Simpson …What is the explanation? Is he guilty?Consideri) Motive; ii) Opportunity; iii) Means for Murder; iv) Time/Place
Evaluating Abductive Arguments
Correctness: Thefactsshould be correctThe glove really did fit. OJ was in LA at the time of murderSimplicity: the explanation should not involve unnecessary entities orcomplexitiesOJ was at the house and committed the murdersOJ remotely controlled a robot that was at the scene and killed NB and RGConservativeness: the explanation shouldn’t force you to revise your beliefs, ifpossible.NB had a religious experience that possessed her to commit suicideFalsifiability: the explanation needs to be incompatible with some possibleoutcomeGod killed NB.
What Kind of Argument is it?
Chapter5 and 6
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Steroid Usage
ExampleBarry bonds was the most dominant hitter in baseball for over 10 yearsBarry Bonds was taking steroidsRoger Clemens was the most dominant pitcher in baseball for over 10 yearsSo, Roger Clemens was probably taking steroidsArgument by Analogy. Is it a strong Argument?Add furthersimilarities to make it strongerBoth dominatedtheir sport at an age when mostathletes losetheir abilities.Bondsgotawhole lotbetter suddenlyand Clemonsdidn'tBonds'sphysical appearancechanged noticeablyandClemons'sdidn't.Strength of argument depends on1. the number ofRELEVANTsimilarities and difference betweenX and Y2.the diversity of the related similarities
Argument for Moral Relativism
Objective moral rules: rules that hold even though people don’t believe themkilling is wrong whether or not people believe it or not; its not a matter of opinionExampleDifferent cultures have different moral rules, codes, principlesAbortion is accepted in some cultures, in others it is notCapital punishmentHonor killingsAnd many moreIf different cultures have different moral rules, then there are no objective moral rulesThere are no objective moral rules, principles, codesDeductive Argument