Logically valid arguments

Question 1

When is a an argument logically valid?

Answer 1

An argument is logically valid iff (if and only if) there is no possible situation in which its premises are all true and its conclusion is false

Question 2

Define an ‘argument’.

Answer 2

An argument is a collection of statements, one of which is designated as the conclusion, and the rest are its premises.

Question 3

What makes an argument logically possible?

Answer 3

The situation can be described with no (logical) contradiction.

Question 4

Can a valid argument have a false conclusion?

Answer 4

Yes.

Question 5

Why can a valid argument have a false conclusion?

Answer 5

Logical validity is not relative to a situation.

Question 6

What makes an argument sound?

Answer 6

• Iff it is logically valid and all its premises are true .
• Whether or not an argument is sound is partly dependent on the situation, since truth values can vary within the situation.

Question 7

Why is determining whether or not an argument is sound partially dependent on the situation?

Answer 7

Since truth values can vary within the situation.

Question 8

What are two another ways of saying that an argument is logically valid?

Answer 8

• Its conclusion of the argument is a logical consequence of its premises.
• Its conclusion is logically entailed by its premises, or that its premises logically entail its conclusion.