Aristotelian Logic & Fashioning an Argument

A Study of Deductive Reasoning

What is Argumentation? Argumentation is a process of

reasoning that asserts the soundness of a debatable position, belief, or conclusion.

Can be used to: Convince other people to accept or

acknowledge the validiy of your position Defend your position from other points of view Question or refute a position you believe to be

misguided, untrue, dangerous, evil, or absurd.

Persuasion vs. Argumentation

Persuasion is a more general term that refers to how a writer influences an audience to adopt a belief or follow a course of action. Pathos, Logos, Ethos…

Argumentation is the appeal to reason…It is more concerned with demonstrating that certain ideas are valid and others are not.

Planning your Essay Topic: ideally, you

should have an intellectual and emotional stake in your topic!

You should keep an open-mind in the research phase. You must be willing to see all sides of the issue.

Purpose: What you expect your argument to accomplish and how you wish your audience to respond.

Thesis: Must take a stand….Must be debatable…AKA Must have a reasonable ANTITHESIS

EVIDENCE1. Facts…2. Opinions…

Interpretations of facts

NOT ALL OPINIONS ARE CREATED EQUAL!

Criteria for evidence1. Relevant…make sure

it’s pertinent to your argument!

2. Representative and typical…Basically, you should avoid cherry-picking evidence and opinions to make your argument look stronger than it is.

3. Sufficient…it needs to be enough!

Refutation When planning

your essay, you should write down all the arguments against your thesis.

Your essay must deal with your opposition’s argument…It must either..

Show they are unsound, unfair, or weak.

If it’s super strong, concede it’s strength…perhaps point out some weaknesses…then move back to showing why your point of view is strong.

Why learn this stuff? Logic = Reasoning Basis of academic

thought Creation of argument

How do I demonstrate logic? Make obvious, explicit

connections between your major thoughts and ideas

You want someone to FOLLOW your train of thought.

Aristotle Worked with syllogisms

Formal system of thoughtProvides a method for connecting ideas together

Syllogism Ex: 1) Wood floats

in water.2) Ships are

made of wood3) Therefore

ships float in water.

Syllogisms #1 and #2 are both a

premise.

#3 is a conclusion

Syllogism Example Reiterated

Premise #1: Wood floats in water.

Premise #2: Ships are made of wood.

Conclusion: Therefore, ships float in water.

Syllogism Practice If all humans are mortal, and all Greeks are humans,

then all Greeks are mortal.

This type of logic isn’t perfect!

All chickens have two legs. Aristotle has two legs. Therefore, Aristotle is a

chicken.=flawed

However, this isn’t the point!

So? When you write an

essay, watch your premises. They should lead to a valid conclusion.

Examples – Fill in the missing

component All trees have

root systems.

Therefore, All trees need nitrogen.

All root systems need nitrogen.

Examples – Fill in the missing

component

All fruits grow on trees

Therefore, all oranges grow on trees

All oranges are fruits

Examples – Fill in the missing

component All bachelor's

are single

Johnny is single, Hence, Johnny is

a bachelor

Ex: Logic w/o syllogism format

Everyday I go to work. This journey from my home to my office takes one hour. My office starts at eight o' clock in the morning. So, if I leave my home at seven o' clock in the morning, I will reach the office in time.

Argument

Validity and Soundness

Argument: Validity A deductive argument is said

to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. Otherwise, a deductive argument is said to be invalid.

Argument: Validity Valid arguments do not require true premises.

Ex: Valid Argument – True premises

Either Elizabeth owns a Honda or she owns a Saturn.

Elizabeth does not own a Honda.

Therefore, Elizabeth owns a Saturn.

Ex: Valid Argument – False premises

All toasters are items made of gold.

All items made of gold are time-travel devices.

Therefore, all toasters are time-travel devices.

Argument - Soundness A sound argument is one that

is not only valid, but begins with premises that are actually true

Soundness A deductive argument is

sound if and only if 1) it is both valid, and 2) all of its premises are actually true.

Otherwise, a deductive argument is unsound.

Ex: Sound argument No felons are eligible voters.

Some professional athletes are felons.

Therefore, some professional athletes are not eligible voters.

QUANTIFIER

S

Practice…