Valid or Invalid? - The Syllogisms

Syllogism 1 of 15

Remember, we're interested only in whether the argument is valid; that is, whether the conclusion follows as a matter of necessity given the truth of the premises. Just select "Valid" or "Invalid" from the drop-down list below, then press Next.

Please select... Valid Invalid

Really Deep Thought

Plato having defined man to be a two-legged, animal without feathers, Diogenes plucked a cock and brought it into the Academy, and said, 'This is Plato's man.' On which account this addition was made to the definition: 'With broad flat nails.'
   --Diogenes Laertius.