Question: Just becuase not P forms a contradiction, doesn't necessarily mean that If P doesn't form a contradiction as well? Can we assume that if an assumption of the opposite leads to logical contradiction that the must mean the original assumption of P also doesn't lead to contradiction?
At 3:22, is that a mistake? After the defn. of contradiction, you show us the statements: "If I'm skilled at poker, then I will win. I won money playing poker. Therefore, I'm skilled at poker.
