A good argument is both

1. Valid

2. Sound

An argument is valid if the conclusion necessarily follows from the truth of the premises.

An example of a valid argument form:

1. If x then y

2. x

3. Therefore, y

Validity doesn’t say whether the premises are true. It only says that the structure of the argument is such a way that IF the premises are true, then the conclusion necessarily follows.

An argument is sound if and only if:

A. The premises are true

B. The argument is valid

An example of a sound argument:

1. All men are mortal

2. I am a man

3. Therefore, I am mortal

Soundness does indeed answer the question of whether the premises are in fact true.

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