Soundness
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
A sound argument is a valid argument whose premises are all true. Soundness guarantees a true conclusion.
Show
"All humans are mortal. Socrates is human. So Socrates is mortal." Valid, with true premises—sound.
Watch for
Valid but unsound is common. Checking the connection is half the work; checking the premises is the rest.