Logical Reasoning & Argument(Logos)Chapter 12

Reasoning from Generalization

•Induction – from specific to general. My Toyota has acceleration problems. Your Toyota has acceleration problems. Bob’s Toyotas have acceleration problems.

Conclusion: Toyotas have acceleration problems.

•Deduction – from general to specific. Smoking cigarettes causes cancer. Marlboro is a cigarette.

Conclusion: Smoking Marlboros causes cancer.

Reasoning from Analogy

•May be either literal or figurative.•Comparing one or more items that are

similar in some way. Tennessee should legalize medical marijuana. Alaska legalized medical marijuana back in

1998.Reasoning: Tennessee and Alaska are both states and are therefore similar.

Reasoning from Cause

•Typically either from cause-to-effect or from effect-to-cause.

From Cause to Effect From Effect to Cause

It’s 10 below zero outside.

I was late for work today.

My car battery won’t start.

My car battery wouldn’t start.

Reasoning from Sign

•Reasoning from circumstances or clues. He drives a Porsche. He must be wealthy. She is wet. It must be raining. My brakes are squealing. I need new brake

pads.

Toulmin’s Model of Reasoning: A “Snapshot” of an Argument

Grounds = evidence or data

Toulmin’s Model of Reasoning

Claim = the point the arguer is trying to prove

Toulmin’s Model of Reasoning

Warrant = links grounds and claim; “Since”

Toulmin’s Model of Reasoning

Backing = Support for the warrant

Toulmin’s Model of Reasoning

Qualifier = Degree of certainty of the argument

Toulmin’s Model of Reasoning

Rebuttal = Reasons that refute the argument; “Unless”

Example using Toulmin Model

Another Example from our Text:

George smokes heavily (G).

Probably (Q)

Heavy smokers are more likely to develop cancer than non-smokers. (W)

Research from U.S. Dept. of Health (B)

George is likely to develop cancer. (C)

Unless George is lucky, or unless a cure is found, or unless he has unusual immunity, or unless he stops smoking. (R)

Our Own Example

_______ was the best movie of 2009.

What evidence supports this claim?

What background information supports the warrant?

What is the connection between the grounds & claim?

How certain are you of this warrant? (Very, probably, certainly, absolutely, possibly, maybe, % sure, etc.)Unless . . .

Fallacies (to name a few)

•Overgeneralization (“Everybody thinks” or “All”)

•False causation (post hoc ergo propter hoc)

•Red herring (irrelevant information)•Either/or (false polarization)•Loaded questions•Arguing in a circle•Ad hominem•Appeal to prejudice•False appeal to authority

Want to know more? Check out http://www.fallacyfiles.org/index.html

A 20 pt. “Think Piece” Assignment:

•Between now and the end of the semester, find a fallacy.

•Write out the fallacy and give the name of the fallacy.

•This assignment does not have to be typed.

•Fallacies are everywhere! (Wait, is that

overgeneralization? No!)