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Please write logic formulas using the syntax previously defined , using (or for brevity,
F), (or
T), ¬, ∧, ∨, and ⇒.Except where directed, use only these connectives.
/home/comp280/bin/waterworld .[Practice problem solution provided.]
Your friend Tracy argues:
It is bad to be depressed. Watching the news makes me feel depressed.Thus, it's good to avoid watching the news.
Regardless of whether the premises and conclusion are true, show that the argument is not, by showing it doesn't hold for all domains.Replace
depressedand
watching newswith expressions which leave the premises true,but the conclusion false (or at least, what most reasonable people would consider false).
Lots of possible counterexamples.
It is bad to be depressed. Doing homework makes me depressed;so it's good to not do my homework.Or,
It is bad for people to be in physical pain. Childbirth causes pain.Therefore childbirth needs be avoided by all people.If the original conclusion is really correct, Tracy needs to elucidate some of his unspoken assumptions.
The flaw seems to be along the lines of,
avoiding bad in the short run may not always be good in the long run(or equivalently, sometimes you have to choose the lesser of two evils).No, you weren't asked to name a specific flaw, and reasonable people can differ on precisely what the flaw is.(And, formal logic is not particularly helpful here.) Nonetheless, uncovering hidden assumptionsin arguments often helps understand the real issues involved.
[Practice problem solution provided.]
An acquaintance says the following to you:
Chris claims knowledge is more important than grades. But she spent yesterday doing an extra-credit assignmentwhich she already knew how to do. Therefore, she's a hypocrite and deserves no respect.
Regardless of whether the premises and conclusion are true,show that the argument is not, by showing it doesn't hold for all domains.Replace
knowledgeand
gradeswith expressions which give you true premises, but a false conclusion(or at least, what most reasonable people would consider false).
knowledgeto something more important, and
gradesto something less important.
Terry claims that encouraging human-rights is more important than playing Tetris.But Terry played Tetris yesterday rather than volunteering with Amnesty International .Most people wouldn't condemn Terry as a hypocrite just because of this; even the most dedicated of people areentitled to some free time. If your friend wants to prove Terry hypocritical,they'll have to provide further evidence or arguments.
Or similarly,
Politician X claims to support science funding, but voted against a proposal to shift all Medicare funds to NASA.
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