chapter 7 - 10/12/2011 Propositional logic Categorical...

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10/12/2011 1 Logic and Reasoning PHIL 102 [12] 10 Oct 2011 Chapter 7 Deductive reasoning: Categorical logic -- Do the homework! -- Propositional logic ≠ Categorical logic How? 1. Propositional logic: simples b compounds 2. t-value of simples b t-value of compounds John sleeps Mary sings If Mary sings , then John sleeps. It is not the case that Mary sings. Propositional logic ≠ Categorical logic How? 1. Propositional logic: simples b compounds 2. t-value of simples b t-value of compounds John sleeps Mary sings If Mary sings , then John sleeps. It is not the case that Mary sings. Propositional logic ≠ Categorical logic How? 1. Propositional logic: simples b compounds 2. t-value of simples b t-value of compounds John sleeps Mary sings If Mary sings , then John sleeps. It is not the case that Mary sings. Unit = simple, atomic statements Dogs bark. All humans are mortal. Differences? Dogs bark b one thought: simple All humans are mortal b not that simple, more than one thought… Dogs bark. All humans are mortal. Differences? Dogs bark b one thought: simple All humans are mortal b not that simple, still one thought…
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2 Dogs bark. All humans are mortal. Differences? Dogs bark b one thought: simple All humans are mortal b All things that are humans are things that are mortal S P ‘Internal’ structure: All things S are things P Dogs bark. All humans are mortal. Differences? Dogs bark b one thought: simple All humans are mortal b not that simple, more than one thought… All things that are humans are things that are mortal S P S, P ≠ statements, claims nothing is said no t-value = categories (properties) = statement ‘compound’ ‘Internal’ structure: All things S are things P All humans are mortal All cats are carnivores All lawyers are afraid of dark All sport cars are expensive = subject (‘things that are…’) = predicate (‘things that are…’) No humans are plants No cats are elephants No lawyer is poor No cheap sport car was own by Elvis = subject (‘thing(s) that are (is)…’) = predicate (‘thing(s) that was…’) Some humans are old Some cats are elephants Some lawyers are courageous Some cheap sport cars are sold on eBay = subject (‘thing(s) that are (is)…’) = predicate (‘thing(s) that was…’) Some humans are not ugly Some cats are not elephants Some lawyers are not courteous Some items are not sold on eBay
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chapter 7 - 10/12/2011 Propositional logic Categorical...

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