Common Fallacies - Part 3

I.               Appeal to Ignorance Argument

Statement A has not been proven false, so it is true.

Or

Statement A has not been proven true so it is false.

Example:

A: Can you prove that aliens visited Earth in the past?

B: No, but…

A: Then aliens haven’t visited Earth because there isn’t any evidence to say they did!

II.            False Dilemma Argument

Either X or Y is true.

Example:

A: Do you like the Woo Sangho and the Minjoo party?

B: Not really.

A: Then you are a supporter of Saenuri.

III.          Red Herring Argument

Argument A is presented by person 1.

Person 2 introduces argument B.

Argument A is abandoned.

Example:

Daughter: “I’m so hurt that Todd broke up with me, Mom.”

Mother: “Just think of all the starving children in Africa. Your problems will seem pretty small then.

Evaluating Inductive Arguments - Strength & Cogency

This is similarly related to validity with deductive arguments.

• Strong inductive arguments are ones where if the premises are true then the conclusion is very likely to be true.
• Think of anything with a 51% (or higher) chance of being true.
• Weak inductive arguments are such that they may very likely be false even if the premises they are based upon are true.
• Think of anything with a 51% (or higher) chance of being false.

Cogent VS Non-cogent Inductive Arguments

This is related to soundness with deductive arguments. 

• If the argument is strong and the premises it is based upon are true, then it is said to be a cogent argument.
• If the argument is weak or the premises it flows from are false or unproven, then it is said to be an uncogent argument.

Evaluating Deductive Arguments - Validity & Soundness

When evaluating deductive arguments, we are concerned with two things; Validity and Soundness

• Valid: an argument is valid if and only if it is necessary that if all of the premises are true, then the conclusion is true. If all the premises are true, then the conclusion must be true. It is impossible that all the premises are true and the conclusion is false.

• Invalid: an argument that is not valid.  We can test for invalidity by assuming that all the premises are true and seeing whether it is still possible for the conclusion to be false.  If this is possible, the argument is invalid.

• Sound: an argument is sound if and only if it is valid and contains only true premises.

• Unsound: an argument that contains one false premise, or more. All invalid arguments are unsound.

Here is a nifty flowchart to help you decide if a deductive argument is valid and sound:

Deductive vs Inductive

Deductive	Inductive
INDICATOR WORDS
Necessarily Certainly Absolutely Definitely Conclusively It follows that… It is logical to conclude that… This logically implies that… This entails that…	Probably/Improbably Plausible/Implausible Likely/Unlikely Reasonable/Unreasonable One would expect that… It is a good bet that… Chances are that… Odds are that….

Deductive Reasoning:

This type of reasoning is “top down,” meaning that it takes a broad, general idea and gets more specific. Deductive reasoning uses facts, rules, definitions or properties to arrive at a conclusion.

Inductive Reasoning:

This type of reasoning is "bottom up," meaning that it takes specific information and makes a broad generalization that is considered probable, allowing for the fact that the conclusion may not be accurate. Inductive reasoning uses patterns from specific activities or examples to arrive at a broad, generalized conclusion.

This infographic may help you to better understand the difference between the two.

Common Fallacies - Part 2

I.               Ad Hominem Argument

1.     Person A makes claim X.

2.     Person B makes an attack on person A.

3.     Therefore person A’s claim is false.

Example:

Tony: “I believe that life occurred on Earth because we happen to be the right distance from the sun and atoms interacted to cause life.” 

Bill: “Tony wants us to believe that the origin of life was an “accident”.  Tony is a godless man who has spent more time in jail than in church, so the only information we should consider from him is the best way to make license plates.

II.            Straw Man Argument

1.     Person A has viewpoint X.

2.     Person B presents position Y, which is a distorted(비뚤어진) version of X.

3.     Person B attacks viewpoint Y.

4.     Therefore X is false/incorrect/flawed.

Example:

Sarah: “GMO crops should be more regulated.”

Tom: “If we take away farmers' ability to grow genetically engineered crops, if we eliminate that option, people will go hungry, nay, people will starve. Unlike my opponent, I choose to use the technology available to us and save lives

III.          Slippery Slope Argument

1.     Event X has occurred (or will or might occur).

2.     Therefore event Y will inevitably (필연적이다시피) happen.

Example:

Tina: “I am for all people being able to marry who they love.”

Colin: “If we allow same-sex couples to marry, then the next thing we know we'll be allowing people to marry their parents, their cars and even monkeys.

Common Fallacies - Part 1

I.                 What Is An Appeal to Authority Fallacy?

Appealing to authority as a reason to believe something is fallacious whenever:

1.     the authority appealed to is not really an authority in this particular subject

2.     the authority cannot be trusted to tell the truth (they are biased)

3.     authorities disagree on this subject (except for the occasional lone wolf)

4.     the author/speaker misquotes the authority.

II.               Questions to Ask When Judging an Authority

1.     Has the authority been identified? Do we know their name, occupation or field of study?

2.     Is their area of expertise legitimate? Is it a real field of study?

3.     Does the authority have sufficient expertise about the subject? Do they have a Masters/PhD in the subject?

4.     Is the claim made by the authority within their area(s) of expertise? Are they talking about a subject in their field of study?

5.     Is the authority free from any bias about the claim? Do they have anything to gain by making this claim?

6.     Is there a consensus among experts in the field about the claim? Do all scientists agree to one viewpoint?

If you can answer YES to all of the above questions, then chances are they appeal to authority is NOT a fallacious appeal to authority.

III.             What is Circular Reasoning?

Circular reasoning is a fallacy in which the premises include the claim that the conclusion is true or (directly or indirectly) assume that the conclusion is true. This sort of “reasoning” typically has the following form.

"A is true because B is true; B is true because A is true."

Circular reasoning can be difficult to detect if it involves a longer chain of propositions.

Detecting Arguments - Premises and Conclusions Part 2

Detecting Arguments - Premises and Conclusions

Premise Indicators		Conclusion Indicators
since because for as follows from as shown by given that seeing that assuming that considering that inasmuch	as indicated by the reason is that for the reason that may be inferred from in view of the fact that may be deduced from may be derived from	therefore hence thus so accordingly in consequence consequently proves that as a result for this reason	for these reasons it follows that we may infer I conclude that which shows that which means that for these reasons it follows that we may infer I conclude that which shows that which means that

Writing Assignment

Using the tables above to guide you, create four sets of premises and arguments of your own. These can be about whatever topic you choose and each one does not need to be related to the previous one. Below is an example you can use to help you finish the writing assignment.

EXAMPLE:

P¹	Long-haired cats shed all over the house.
P²	Long-haired cats have a lot of fleas.
C	You should not get a long haired cat.

Cats with long hair shed all over the house so you shouldn’t get a long-haired cat. I have heard that they also have lots of fleas.