exam 1 logic

Question 1

Define the term Argument

Answer 1

An attempt to prove something. A group of statements where some are offered in evidence for another.

Question 2

Define the term “Valid Argument”

Answer 2

If all the premises are true then necessarily, the conclusion must be true.

Question 3

Define the term “Sound Argument”

Answer 3

A valid argument, where the premises are also true. “Valid” + “Logical” Facts and Logic together.

Question 4

To determine validity, should we ask the question,” are the premises true and the conclusion false?”

Answer 4

NO. We should ask COULD all the premises be true, WHILE the conclusion is false.

Question 5

Can arguments be true or false?

Answer 5

No, T/F is applied to statements or premises, not arguments. Arguments are valid, invalid…sound/unsound

Question 6

Can statements be valid or sound?

Answer 6

No. Statements are T/F. Arguments are valid/invalid, sound/unsound.

Question 7

Is it Is it possible to know whether an argument is valid without knowing the truth values of the premises and conclusion?

Answer 7

Yes, by applying "IF".
Consider:
All members of the club are Irish.
Tom is a member.
\:. Tom is Irish
Apply if, so regardless of the truth values, T,T,F is impossible. If all members, If Tom, then Tom.

Question 8

Suppose a statements contains all false statements. Is it valid or invalid?

Answer 8

It could be either.
Valid:
All lawyers are crooks
All crooks are rich
\:.all lawyers are rich.
Meets the IF test.
Invalid:
Its sunday
Its august
\:.its 2013
not necessarily true.  Can have a TTF

Question 9

You have an argument with all true statements. Can it be unsound?

Answer 9

Yes,
It can be unsound by being invalid.
Its Wed
Its Sept
\:. Its 2013
lacking TTT, TTF possible

Question 10

Logic is subject invariant. How so?

Answer 10

Validity is independent of subject matter. It is the pattern of reasoning, not the content that matters.
Pattern remains the same regardless of changes in subject matter.

Question 11

Two valid argument forms. Illistrate validity with “Dollar” example

Answer 11

Modus Ponins "MP". 
If I have a dollar, then I have more than .50.
I have a dollar
\:.I have more than .50
Modus Tollens
If I have a dollar, then I have more than .50
I dont have more than .50
\:.I dont have a dollar.

Question 12

Two formal fallacies. Illustrate with “Dollar” example.

Answer 12

Fallacy of denying the antecedent.
If I have a dollar, then I have .50
I dont have a dollar
\:.I dont have .50
.85 is not dollar, but is .50
Fallacy of affirming the consequent:
If I have a dollar, then I have .50
I have .50
\:. I have a dollar
.85 is .50 not dollar

Question 13

3 requirements of good proof

Answer 13

factual
logical
informative

Question 14

Distinguish errors of fact from errors of reasoning.

Answer 14

Consider:
Its Wed
Its Sept
\:.Its 2013
All the facts are right, however breakdown in reasoning.
Consider:
All Lawyers are crooks
All crooks are rich
\:.All lawyers are rich
Reasoning is accurate, however it is not factually true.

Question 15

Define the direct method for proving arguments invalid. Give example

Answer 15

Show how its possible for all the premises to be true while the conclusion is false.
Consider:
If Tom is guilty, Mary is guilty
Tom is not guilty
Mary is not guilty
Suppose: Tom might always work with Mary. this makes the 1st premise true.
What if Mary did it alone?
2nd premise is true, but conclusion is false.