Logic 101 (#31): Constructive Dilemma

Logic 101

Constructive dilemma is a logical rule of inference that says if P implies Q, R implies S, and P or R is true, then Q or S is true as well. Essentially, the constructive dilemma passes the disjunction through two conditional statements. For example, if the statements

“If I am running, I am happy.”

and

“If I am sleeping, I am dreaming.”

and

“I am running or sleeping.”

are true, then it must also be true that I am happy or I am dreaming.