This lecture discusses the ancient Greek philosopher Aristotle' work, On Interpretation, focusing on his discussion of contrary and contradictory propositions, both of which are ways in which propositions are opposed to each other, with contradictories being more opposed to each other than contraries. With contrary propositions, if they are universal, one of them must be false (and it is possible for both of them to be false). With contradictory propositions, one of them must be true and the other false.To support my ongoing work, go to my Patreon site - www.patreon.com/sadlerIf you'd like to make a direct contribution, you can do so here - www.paypal.me/ReasonIOYou can find over 4,000 philosophy videos in my main YouTube channel - www.youtube.com/user/gbisadlerPurchase Aristotle's On Interpretation - amzn.to/3nS55ud