Soundness
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
An argument is sound when it is valid AND all its premises are actually true. Sound arguments guarantee true conclusions.
Show
"All humans are mortal; Socrates is human; so Socrates is mortal." Valid form, true premises: sound.
Watch for
Sound is the gold standard. Valid is only half the job.