The Language of Argument

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The Language of Argument

I think that there is either a six pack of Molson Golden in the fridge upstairs or a six of Sam Adams in the fridge downstairs. Informed sources tell me that there are no Molsonsleft in the house. So, there is a six pack of cold Sam Adams waiting for us there.

Put the argument in standard form.

There is either a six pack of Molson Golden in the fridge upstairs or a six of Sam Adams in the fridge downstairs.

There are no Molsonsin the house.


There is a six of Sam Adams in the fridge downstairs.

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The Language of Argument: Validity, Truth, And
Soundness

•An argument is valid just in case it is impossible for all of its premises to be true when the conclusion is false.
•A valid argument by definition cannot have true premises and a false conclusion. So, if the premises of a valid argument are all true, then the conclusion must be true as well. The information contained in the premises is sufficient to rule out the possibility of the conclusion being false.

•We say that the premises of a valid argument implyor entailthe conclusion.

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The Language of Argument: Validity, Truth, And
Soundness

There is either a six pack of Molson Golden in the fridge upstairs or a six of Sam Adams in the fridge downstairs.

There are no Molsonsin the house.


There is a six of Sam Adams in the fridge downstairs.

This is a valid argument. If there are no Molsonsin the house, there are none in the fridge upstairs. But then, given the first premise, we may derive that there’s a six of Sam Adams in the fridge downstairs.

3
The Language of Argument: Validity, Truth, And
Soundness

People who studied a lot are people who got an “A” on the test.

Mary did not study a lot.


Mary did not get an “A” on the test.

Valid or invalid?

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The Language of Argument: Validity, Truth, And
Soundness

Janet is not both at work and at home.

Janet is at work.


Janet is not at home.

Valid or invalid?

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The Language of Argument: Validity, Truth, And
Soundness

Some Republicans are rich.

Some rich people are criminals.


Some Republicans are criminals.

Valid or invalid?

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The Language of Argument: Validity, Truth, And
Soundness

Sara is brave.

Only the brave die young.


Sara will die young.

If I just tell you that the premises are true, this is insufficient for assessing the truth of the conclusion. The truth of the premises do not rule out the possibility of Sara living to an old age. Do you see why? (Hint: the second premise says that all who die young are brave and not that all who are brave die young). Since the truth of the premises do not conclusively establish the truth of the conclusion, the argument is invalid.

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The Language of Argument: Validity, And
Soundness

More technical jargon: An argument is soundjust in case it is both valid and all of its premises are true.

5>3The capital of Michigan is Flint.

2>1Flint is not Lansing.


5>1•
The capital of Michigan is not Lansing.

False: If an argument is valid, then it is sound.

True: If an argument is sound, then it is valid.

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Validity, Truth, and Soundness
Demonstrations

The Language of Argument: Argument Markers
Argument Markers are expressions that may flag components of an argument.

For example, “because”, “since”, and “for” are premise indicators. The expressions “therefore”, “hence”, and “thus” are conclusion indicators.

An expression is not guaranteed to always be an argument marker.

(i) Frank is happy, so he must have eaten.

(ii) I love you so much.

The word “so” in (i) is an argument marker, but not in (ii).

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Argument Markers Demonstrations

The Language of Argument: Speech acts performed in
Argumentation

Argumentative performatives are explicit performatives used to make a move in an argument (e.g., “I conclude that…”, “I assume for the sake of argument that…”, “I...
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