Lesson Four: The Impossible Dream

In 1950, Kenneth Arrow made a very surprising discovery. He found that no voting method can ever satisfy these three conditions. That's not just the voting methods we know of now, but any voting method anybody might think of in the future as well. This fact is known as Arrow's Impossibility Theorem. This discovery was a major factor in Arrow winning the Nobel Prize in Economics.

In simple terms, Arrow's discovery means that we can never find a voting method that does everything we want. But we can still look for methods which are better in some respects. One which has gained some support recently is called approval voting. It will be described in Lesson Five.


Lesson Five