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Logic for Intro

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Michele Merritt

on 26 August 2018

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Transcript of Logic for Intro

Logic and Reasoning
A Few More Strategies
Argument By Analogy
Name that Fallacy!
1. God exists because the bible says so and the bible is true because it was written by God.

2. The death penalty should be permitted. After all, overpopulation is a problem.

3. Teacher, you should give me a better grade on the assignment. If you don't, I will lose my 4.0, not graduate with honors, not get the job I want, and my life will be ruined.

4. Ashtrays and lung cancer are strongly correlated. Therefore, ashtray use causes lung cancer.

5. Having only one penny to your name is better than nothing. Nothing is better than ice cream. Therefore, having only one penny to your name is better than ice cream.
Logic: The Science of Argument
Flaws, mistakes, illegal inferences, defect of reasoning
Writing Effective Argumentative Essays
Ask yourself:
1. What do I want to prove?
2.What kind of argument will I construct??
3. If deductive, does the supposed truth of
my premises necessitate the conclusion?
Are my premises actually true?
4. If inductive, do I have evidence for all
my premises? Does the evidence actually
support the conclusion?
Many, Many ways to go Wrong
Mere Assertion Begging the Question Circular Reasoning
Irrelevancies Ad Hominems Unclear/Changing Meanings (Equivocation or
Amphiboly )
Red Herrings Complex Questions Unqualified Appeal to Authority
Slippery Slope Straw Man Attacks Emotional Appeals
Appeal to Force Misidentification of Cause Post Hoc Ergo Propter Hoc
Defending your Position
1. Counterexamples?
2. Have I committed
any fallacies?
3. Am I being clear
with each and every term
I use?
Philosophical Debate
What is an argument?
Consider this scenario:
Bob and Julie are arguing about the death penalty. Julie says she is in favor of allowing it and cites several reasons, including 1. prisons cost too much money, 2. some crimes are deserving of death, and 3. the world is overpopulated anyways. Bob responds to her argument by saying he disagrees. First of all, he claims, murdering murderers does not solve problems. Second, he cites evidence that it is not in fact the case that imprisoning people costs more than killing them. And third, he tells Julie she can't really have a good argument regarding all of this because she is a dumb blonde.

Take a minute to think about what claims can be supported by good reasoning here and which cannot.
An argument is a group of statements (premises), one or more of which lead up to and purportedly give evidence for accepting a final statement (the conclusion)
Reductio Ad Absurdum
Descartes' Evil Demon:

I doubt I exist
But doubting is thinking
Thinking implies someone is doing the thinking
I am the one doing the thinking
Therefore, I exist.
Can be deductive or inductive
Start with a THESIS - the thing you are trying to prove.

Then list as many reasons as you can think of to support that thesis.
Types of Inference (Inference = the logical step you take from premises to conclusion)
Mathematical arguments, e.g.
Scientific Method, Stats, etc.
Above all: be sure to address any potential objections to your view and AVOID COMMITTING FALLACIES!
Quiz: Define "argument".
Full transcript