I'm trying to to determine whether the following is a tautology, contingency, or contradictory:
(p ⊃ q) ∨ (q ⊃ p) .⊃. (r .⊃. s ⊃ r)
This is school work. I'm getting that it's a tautology, but only through looking at patterns of solutions of textbook problems and exercises. I would like to know what exactly is meant by the dot prior and after the material implication (.⊃.)?
I understand that material implication - in a truth table - has false only when p is true and q is false. I also understand the or operator where it's true where either both or one of the two, namely: p or q is true. I just need to understand what the dots are supposed to mean. I couldn't find good explanations online.