Arguments and inductive logic PDF

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Matthew Seacord...

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Phil 102-3009 1/25/18 #9021 Pg. 1

Arguments: Attempting to provide reason for a conclusion  Deductive arguments – Conclusive support for its conclusion (meaning its valid) If the premise is true, the conclusion must be true  Inductive arguments – Probable support for its conclusion (meaning it is possible that the premises are true and the conclusion is false) Example of a deductive argument : All cable news is terrible, CNN is cable news. Therefore, CNN is terrible. Example of an Inductive argument: All cable news is terrible, all reality shows are terrible. Therefore, all cable news shows are reality shows.

Inductive  Strong – It provides probable support for the conclusion  Weak – fails to make the conclusion more probable Most TV shows are bad, FRIENDS was a TV show. Therefore, FRIENDS was probably bad. Good Arguments  Deductive -- Must be valid and have true premises = sound  Inductive – strong and true premises = Cogent NECESSARY + SUFFICIENT CONDITIONS

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Necessary: Are something that must be there for a thing to be an X. X = bachelor: unmarried and male Bachelor – individually unnecessary & jointly sufficient Sufficient: Something that guarantees a thing is an X. X = student enrolled in a course at College.

Identifying and Evaluating/ Judging Arguments: Is it deductive or inductive? Deductive – “Certainly”, “absolutely”, “it’s logical”. Does it work? Inductive – “chances are”, “it is plausible that”, “it is likely”.

Common Argument Types If X, then Y If – antecedent (P) Then – Consequent (Q) Modus Ponens  If P, then Q  P therefore Q Modus Tollens  If P, then Q  Not Q, therefore not P

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If I have to visit my in-laws, I will drink too much. I did not drink too much this weekend, therefore I did not have to visit my in-laws

Affirming the Consequent  If P, then Q  Q I drank too much this weekend  P therefore I visited my in-laws Denying the Antecedent  If P, then Q  ~~ P I didn’t visit my in-laws  ~~ Q therefore I didn’t drink too much. Hypothetical Syllogism – Deductively argument forms  If P, Then Q  If Q, Then R  Therefore, If P, Then R If I go to the store, then I will buy fruit. If I buy fruit, then I will buy apples. Therefore, If I go to the store, then I will buy apples.

Disjunctive Syllogism  Either P or Q  Therefore, if not P, then Q

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I will buy apples or bananas I did not buy bananas Therefore, I bought apples...