Condorcet's Paradox

Let's say Derek, Jac, and Patrick are deciding on which drink they should buy. If the choice is between Dr. Pepper and Coke, they pick Dr. Pepper 2 to 1. If the choice is between Coke and Pepsi, they pick Coke 2 to 1.

So they like Dr. Pepper better than Coke and Coke better than Pepsi. Does it follow that they like Dr. Pepper better than Pepsi? No! They prefer Pepsi to Dr. Pepper 2 to 1!

This apparent paradox was first noted by the Marquis de Condorcet in the 18th century, and it is named the Condorcet Paradox in his honor.