Lecture 9

Question 1

okay for this lecture, the total is 13 slides, 1-7 is not included cuz it just examples and its better to acc see them

Question 2

To test whether an argument is invalid,

Answer 2

we do not need to set up a whole truth-
table: after all, we only need to try to find a row where all the premises are true,
and the conclusion is false.
( check slide 8)

Question 3

What are the six steps of short step method

Answer 3

1. Write out the symbolized argument in a single row.
2. Above the main connective for each premise, write “T”.
3. Above the main connective for the conclusion, write “F”.
4. Assign truth-values to the variables in the conclusion to make the
   conclusion false. Assign these truth values to the same variables
   elsewhere.
5. Consistently assign truth values to variables in the premises.
   (Begin with ones where specific truth values are “locked in”.)
6. Try to make assignments that yield all true premises and a false
   conclusion. If you can, the argument is invalid.

Question 4

How many steps are there in the short step method

Answer 4

6

Question 5

Whats step one in the short step method

Answer 5

Write out the symbolized argument in a single row.

Question 6

Whats step 2 in the short step method

Answer 6

Above the main connective for each premise, write “T”.

Question 7

Whats step 3 in the short step method

Answer 7

Above the main connective for the conclusion, write “F”.

Question 8

Whats step 4 in the short step method

Answer 8

Assign truth-values to the variables in the conclusion to make the
conclusion false. Assign these truth values to the same variables

Question 9

Whats step 5 in the short step method

Answer 9

Consistently assign truth values to variables in the premises.
(Begin with ones where specific truth values are “locked in”.)

Question 10

Whats step 6 in the short step method

Answer 10

. Try to make assignments that yield all true premises and a false
conclusion. If you can, the argument is invalid.

Question 11

How do we know an argument is invalid in the short step method

Answer 11

Our job is still to try to find a row where all the premises are true, and the conclusion is false. If we can, then we know this
is an invalid argument.
The only new thing we’re doing is distinguishing between various ways in which the conclusion can be false. These are
numbered 1,2, and 3.