Validity & Form

Question 1

Hypothetical Syllogism

Answer 1

If P, then Q.
If Q, then R.
Therefore,
If P, then R.
If you party every weekend you will be too tired to study.
If you are too tired to study then you will fail the exam.
therefore,
if you party every weekend then you will fail the exam.

Question 2

Simplified Dilemma

Answer 2

Either P or Q.
If P then R
If Q then R
Therefore, R
Either I will go to Thailand or india.
If I go to Thailand I will get a suntan
If I go to India I will get a suntan
therefore, I will get a suntan.

Question 3

Disjunctive Syllogism

Answer 3

Either P or Q
It is not the case that P
therefore Q - Denying the antecedent - Fallicious.

Question 4

Modus Ponens

Answer 4

If P then Q
P
therefore Q
Affirming the antecedent - Valid

Question 5

Modus Tollens

Answer 5

If P then Q
not Q
Therefore not P - Denying the consequent - Valid.