Lessons in Logic 4: Validity, Soundness, Strength, Cogency, and Their Opposites

If you wanna study logic, you gotta learn the vocab. A proposition is either true or false, and that's it. But an argument is:
--valid or invalid;
--sound or unsound;
--if invalid, strong or weak;
--if weak, uncogent;
--and, if strong, either cogent or uncogent.