3.1: Fallacies (Part 1)

Fallacies

• In logic, we focus on evaluating arguments.
• Mostly, we will use formal tools to judge whether an argument is valid.
• In this section, we will learn about different patterns of bad reasoning that people can exhibit in their arguments.

Fallacies

• Suppose a child is trying to prove to his friend that he is the smartest kid in the class:
  "I'm the smartest kid in the class. My dad says so."

Fallacies

"Milk is bad for you. I heard someone say that on the internet."

Both involve appeal to authority.

Fallacies

• Appeal to Authority: an argument that says that the conclusion must be true because somebody else says that it is true.

"Milk is bad for you. I heard someone say that on the internet."

Fallacies

• Appeal to Force: An argument that attempts to convince the opponent by using, or threatening to use, force.

Example:
"I should be the leader of this group. If anyone disagrees with me, I'll break their legs!"

Fallacies

• Appeal to Pity: An argument that attempts to convince the opponent by evoking sympathy or pity.

Example:
"I should be the leader of this group. If I don't get to be the leader, I'll feel so sad and pathetic!"

Fallacies

• Subjectivism: An argument which says that the conclusion must be true because I think it's true!

Example:
"I should be the leader of this group. I just know I should and I'm always right about these feelings!"

Fallacies

• Straw Man: A counter-argument that is really responding to a much weaker version of the original argument.

Example:
"Global warming doesn't exist! It doesn't get hotter every single day of the year!"

Fallacies

• Slippery Slope: An argument which says that if one event occurs, a whole series of other events will follow it.

Example:
"If they let people into the restaurant without a tie on, then pretty soon people will want to eat here in the nude!"

Fallacies

• False Alternative: An argument which forces the person to choose between two options, but it is a "false choice" (those aren't the only two options, e.g.).

Example:
"Either we stop at the next restaurant we see, or I'm going to die of hunger."

Fallacies

• Tu Quoque: An argument which accuses the other person of being a hypocrite.

Example:
"You're accusing me of cheating on the exam? I saw you copying the answers from Dave!"

Fallacies

• Ad Hominem: An argument which tries to win by attacking the personal qualities of the opponent, rather than their reasoning or claims.

Example:
"I didn't cheat on the exam! You're a liar and you stole money from your own brother!"

Fallacies

• Appeal to Authority
• Appeal to Force
• Appeal to Pity
• Subjectivism
• Slippery Slope
• Straw Man
• False Alternative
• Tu Quoque
• Ad Hominem