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Logical Fallacies

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Samuel Sloan

on 31 March 2015

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Transcript of Logical Fallacies

Fallacies of Relevance
if it has not been proven wrong, then it must be right, or vice versa
Ex: No one has ever proven the easter bunny doesn't exist - he MUST be real; this new system of healthcare has never been implemented - obviously, it's not going to work.
Ad ignorantium -
appeal to ignorance
does not follow; the premise & the conclusion are unrelated – the conclusion may be true or false, but the “proof” is unrelated or nonsensical
Ex: You argument is wrong because my foot is toast; Person 1: Hey, you wanna go swimming? Person 2: I've got a lovely bunch of coconuts.
Ad populum -
Non sequitur
a distraction from the actual argument at hand
Ex: Tim and Bob are arguing about health care reform. Tim asks "how can we afford NOT to provide preventative medicine in this country?" Bob responds, "I don't know about that - I believe in freedom-why would you suggest something that is opposed to freedom and free-choice?"
red herring
because it has always been this way, it must be right; also includes appeals to authority
Ex: We have never had woman president, so we will never have a woman president; Democracy is the only form of government we've had, so it's the only one that makes sense.
Ad verecundiam -
appeal to tradition
Fallacies of False Reasoning
the newest ideas must be the correct ones simply because they are new
Ex: Twitter has to be the best way to communicate, it's the most recent medium; Have you heard of the new bio vac diet? It's the best way to loose weight!
Appeal to novelty
if everyone believes it or accepts it, it must be true
Ex: Everyone thinks the iPhone is the best phone, it has to be because everyone has one; Jumping off a bridge, because everyone else is...
argument based on mis-representing an opponent's position; first, a complex argument is simplified, then the person attacks the simplified argument, rather than engaging the complexity.

Ex: In a debate, Bob gives a detailed description of 20 different ways people in today's economy find themselves temporarily jobless, and Tim responds, "Well, as you can see here, Bob is interested in giving handouts and making welfare queens."
Straw Man Argument
speaker suggests that there are only two options, when more exist

Ex: If you're having relationship problems you only have two options: A, Drink or B, Get the hell Out! ; You can either plea guilty to the charges or rot in this jail cell for the rest of your life.
False dilemma/dichotomy
making a claim that assumes what you are trying to prove; saying the claim is true without proof; "leading the witness"

Ex: You've got to be interested in me, right? You want to do this, don't you? You committed the crime, didn't you? Why wouldn't you want this beautiful diamond?
Begging the Question
comparing two things that are not similar or comparable
Ex: Presidential candidates are just like every day people
Ex: Going through the TSA is like going to a day spa
Faulty Analogy
assuming the worst possible outcome for a cause
Ex: If this girl doesn't call me back, I'm going to spend the whole night alone, then I'm never going to get a date, then I'm going to have to move back in my parents' basement and become a crazy cat lady and a brony and no one will ever love me again, except other bronies...
Ex:If my paper is late, my world will end.
Slippery Slope
Fallacies of
Inadequate Evidence

“after this, therefore because of this;”
false cause; confuses a chronological (sequential or time-based) relationship with a causal one (cause effect), or vice-versa;
The idea that B happened after A, so A must cause B

Ex: That guy started smoking pot, then three months later, I found him being a prostitute on the street. It must have been the drugs...

Ex: The rooster crowed, then the sun rose, so the rooster causes the sun to rise.
Post hoc, ergo propter hoc
related to inductive reasoning; stereotyping; using too small a sample size as proof

Ex: I saw a homeless man get drunk with money I gave him for "medicine" - all homeless men are liars

Ex: My one blond friend doesn't know anything about politics - blonds can't do political science
Hasty generalization
Fallacies of Personal Attack
name-calling; personal attack; casting doubt on the ethos of an opponent/speaker/argument instead of addressing their opposing ideas

Ex: You shouldn't vote for the other candidate because he is a liar and a thief.

Ex. Sally is a poopy head.

Ex. Tim doesn't believe in family values, that makes him an atheist who's going to hell.
Ad Hominem -
to the person
someone or their ideas are suspect because of who/what they are associated with or share qualities with
inverse is “Honor by Association”

in which something/someone in an argument is considered to be reputable because of its/their associations

Ex: You were caught with some kids who were doing drugs, so you must be a drug user too.

Ex: You're in that charity organization, so you must do service for the community all the time...
Guilt by Association
These hurt your credibility and your ethos.
Be on the lookout for these in your persuasive argumentation
Do people perform speeches with these? Yes all the time, part of the reason politicians are thought of as "liars" or users of "empty promises"
Being aware of logical fallacies is part of being an ETHICAL speaker and listener.
Logical Fallacies
- Errors in Logical Reasoning
Comm. pgs: 54-58
Texas Sharpshooter Fallacy:
Occurs when someone has tons of data about a given topic, but chooses to draw a circle around a very small set of that data in order to prove their point (Similar to the idea of "cherrypicking data")
Whenever you use a persuasive argument in order to prove your point, the issue of logical argumentation comes up.

A good, logical argument:
Uses good premises
(ones you believe are true and which are relevant to the subject being discussed.
Provides good support
for your conclusion
Addresses the most important or relevant aspects
of the issue at hand
Does not make claims that are unable to be supported
with data/evidence.
Full transcript