The Language of Argument

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.

1
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. 2
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?

4
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.