2. Validity and soundness

Question 1

Logically Possible (3)

Answer 1

1) The weakest, most inclusive kind of possibility
2) What can be thought coherently
3) True in at least one possible situation

Question 2

Logical Necessity (3)

Answer 2

1) The strongest kind of necessity
2) Not possibly not
3) True in all possible situations

Question 3

Validity (2)

Answer 3

1) Necessary truth preservation from premises to conclusion.
2) Independent of de facto truth

Question 4

Propositions (2)

Answer 4

1) Premises and Conclusions that are true or false
2) Not commands, questions and exclamations

Question 5

Consistent (2)

Answer 5

1) If propositions can be true together
2) If there is a possible situation where all propositions are true

Question 6

Inconsistent (2)

Answer 6

1) If propositions cannot be true together
2) If no possible situation where all proposition are true

Question 7

Valid Argument

Answer 7

Premises and the negation of its conclusion are inconsistent
EX:
{all logicians are smart, L is a logician, L is smart}

Question 8

Invalid Argument

Answer 8

Premises and the negation of its conclusion are consistent
EX:
{all logicians are smart, E is smart, E is not not a logician}

Question 9

Equivalence (2)

Answer 9

1) True in exactly the same possible situations
2) Same building blocks

Question 10

Validity (Cases)

Answer 10

Exists:
P: All True C: True
P: At least one false C: True
P: At least one false C: False

BUT NEVER ABSOLUTELY NEVER
P: ALL TRUE C: FALSE

Question 11

Invalidity (Cases)

Answer 11

P: All True C: True
P: At least one false C: True
P: At least one false C: False

ALWAYS INVALID
P: ALL TRUE C: FALSE

Question 12

Soundness

Answer 12

1) Valid inference-step
2) True (truth) premises