A rule of inference in propositional Logic. Written as CD for short. Constructive dilemma is used to break up a dilemma. It goes like this:

(P→Q) ∧ (R→S)
Therefore, Q∨S.

"If it rains, you'll get wet" (P→Q); and "If it's cold, you'll shiver" (R→S).
"Either it's raining" (P), or "it's cold" (R).
Therefore, you're either wet, or you're shivering.

In this case, 'or' is not 'xor', so you might very well be both wet and shivering.

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