Critical Thinking, Logic, and Skepticism for Children Course: Lesson 3 (Types of Reasoning)

Lesson 3:

Review Homework.  Let each child read their essay, and explain how it felt to think as someone else.

Inductive and Deductive Reasoning:

The Premise:

A premise is a statement that an argument claims will induce or justify a conclusion.[1] In other words, a premise is an assumption that something is true. In logic, an argument requires a set of at least two declarative sentences (or “propositions”), known as the premises, along with another declarative sentence (or “proposition”), known as the conclusion. This structure of two premises and one conclusion forms the basic argumentative structure.

http://www.youtube.com/watch?feature=player_embedded&v=VRZk62QNOsM

The Fallacy:

A fallacy is a deceptive, misleading, false notion or belief (can be based on true statements in the wrong order).

An informal fallacy is an error in reasoning that does not originate in improper logical form. The logic may be perfectly deductive or inductive, but the conclusion false.

Example:

Earth is a planet.

All planets revolve around a star.

The earth revolves around the sun.

Therefore, the sun is a star.

 

Bad example:

All dogs have four feet.

It has four feet.

Therefore, it is a dog.

 

Inductive Reasoning:

Inductive reasoning is a kind of reasoning that constructs or evaluates general propositions that are derived from specific examples. Inductive reasoning contrasts with deductive reasoning, in which specific examples are derived from general propositions.

Example:  All the tigers observed in a particular region have yellow stripes. Therefore, all the tigers native to this region have yellow stripes.

Visual example:

Look at the patterns below. Can you draw the next figure or next set of dots using inductive reasoning?

The answer should look like this:

Example:

The sun has risen every day in recorded history.

Therefore, the sun will rise tomorrow.

Weak Example:

Everyone I know loves Batman.

I know you.

You must love Batman.

 

You always wear purple shirts.

The next time I see you, you will be wearing a purple shirt.

‘Being rational’ is to act upon reason or understanding. Rational explanation or rational behavior is an act where the explanation/behavior is based on hard facts which do not change according to the whims and fancy of the ‘rational’ person.

Rationalization, on the other hand involves the twisting and distortion of facts and reasoning to suit your own purposes (in the objective world, this is called cheating).

Rational:  I am hungry.  I have eaten my vegetables, meat, and dinner. I like cookies.  There is a cookie for me. Therefore, I should eat a cookie.

Rationalizing: I ate the cookie because I need cookies to keep me strong.

http://www.youtube.com/watch?v=9b3KM2p1nHs

Activity:  

Identify the premise, any fallacies, and whether the statements are deductive or inductive.

1)  “Senator Jones suggests reducing the attack submarine program. I disagree entirely. I can’t understand why he wants to leave us defenseless like that.”

2) Bill and Jill are arguing about cleaning out their closets:

Jill: “We should clean out the closets. They are getting a bit messy.”

Bill: “Why, we just went through those closets last year. Do we have to clean them out everyday?”

Jill: “I never said anything about cleaning them out every day. You just want too keep all your junk forever, which is just ridiculous.”

 

3) Every time Dorothy drinks milk, she gets a rash around her mouth. Therefore, milk causes a rash on Dorothy.

4) “When chimpanzees are exposed to rage, they tend to become violent. Humans are similar to chimpanzees, and therefore, they tend to get violent when exposed to rage.”

5) The dog would have barked if it saw a stranger. It didn’t bark, so it didn’t see a stranger.

Inductive and deductive thinking are difficult even for adults. Many adults make mistakes in rational thinking all the time.  In fact, in the media you can often see many fallacies made by politicians, advertisers, and others who are highly respected. You don’t have to be perfect at this, but you will be more successful the better you get at deductive and inductive thinking.

Homework:

Observe a conversation between two people.  Write down the statements that push for a conclusion. Identify the premises used. Identify if they person used inductive or deductive thinking.  Identify any fallacies.

Media examples of bad induction and deduction, faulty premise, and fallacies:

http://www.youtube.com/watch?v=sT_VhDrn8NY

http://www.youtube.com/watch?v=LKQiGjYu_6w

Conclusion:

We will all be better able to identify rational decisions and not be misled by practicing inductive and deductive reasoning. It takes practice as these ideas are hard for everyone.  The benefits of learning it outweigh the costs of effort.

This entry was posted in Critical Thinking course for Kids. Bookmark the permalink. Last edited by EmmaHS on June 11, 2013 at 1:16 am

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