PHL 214 Lecture Notes - Lecture 5: Flowchart, Modus Ponens, Modus Tollens
5 Feb 2016
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A valid argument doesn"t have to have true premises/conclusions, what matters is the relationship. A sound argument is deductively valid and all its premises are true, therefore sound- conclusion always true. Cannot be true p, false c = automatically invalid. True c, false p, valid but not sound: all reptiles are mammals. Strength: inductively strong if and only if (iff) given true premises, conclusion probably true. Cogency: iff argument is inductively strong and all the premises are true. Therefore a is corrupt (insert argument classification flowchart) Pattern: logical structure common to many arguments: conditional statement: statement of the form. Antecedent that follows if", consequent that follows then". Can have statements where consequent is spoken first, but is still playing role of after : disjunctive statements: statement of the form. Compound statements with two parts are called disjuncts . Valid conditional argument patterns: modus ponens (affirming the antecedent) If liberals win the election, then a is prime minister.
