Deductive Validity

Question

4(a) Determine whether the argument is valid, and give a reason why.

Collingwood can’t make the final unless the Wallabies defeat Richmond. The Wallabies defeated Richmond therefore Collingwood will make the final.

Select one:

a. The argument is valid, it has the valid form of modus ponens.

b. The argument is invalid, the Wallabies would never play Richmond.

c. The argument is invalid, there may be other reasons why Collingwood won’t make the final.

d. The argument is valid, the premises are all true and so is the conclusion.

e. The argument is invalid, the premises are not true so the conclusion must be false.

f. The argument is valid, the premises can’t be false and the conclusion true.

4(b) Choose the generalised form that represents the argument.

A = Collingwood makes the final.

B = The Wallabies defeat Richmond.

Select one:

a.

1. If Not B then Not A.

2. B.

Therefore,

C: A.

b.

1. If Not B then A.

2. B.

Therefore,

C: A.

c.

1. If B then A.

2. B.

Therefore,

C: A.

d.

1. If A then B.

2. Not B.

Therefore,

C: Not A.

Answer 1

C, it's invalid. Defeating Richmond just made it possible that Collingswood could make the final, but not that it would make the final. since there are other reasons it may not make the final

A is the general form of the invalid argument