Cui bono

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Qui bono (properly cui bono?) is Latin for "who benefits?"

It is the single most important question to ask when evaluating any (usually political or criminal) manoeuver. After all, humans are inclined to support, if not cause, actions that benefit them.

However, this is not a particularly wise thing to do when answering a question of a scientific or medical nature, as these fields are based in fact and empirical evidence. Special interest groups benefit from scientific advancements, for sure, but the underlying assumption in this case is that everyone else will as well. This has not stopped some from questioning motives anyway. Take Paul Brodeur [1], who got a significant part of the world afraid that cell phones and power lines cause cancer because people do not understand the difference between ionizing and non-ionizing radiation.[2]

Reductio ad absurdum of cui bono[edit]

While it's always good to ask "cui bono?", it can be taken to ridiculous extremes. Many conspiracy theories are built using this line of reasoning and then working backward from the conclusion by relying on post hoc reasoning. A classic example is 9/11 conspiracy theories. Cui bono? The Bush administration, of course, so they must have done it! Isn't it suspicious that 9/11 just happened to give cover to their plans for war?

Cui bono should also never be the only question to ask, as benefits from an event are never enough to directly implicate one with an action. If it is only asked who benefits from something and other factors are not taken into account, ridiculous conclusions can be extrapolated. Take the following example:

Emperor Penguins thrive in extremely cold climates. Many other species don't. Therefore it is obvious that Emperor Penguins have the most to gain from a cold Antarctica, hence Emperor Penguins are responsible for the cold in extreme southern latitudes.

It could - and should - have been asked whether Emperor Penguins even have the means to make it cold in Antarctica, which they obviously don't.

A different example would be the moon landing hoax theories that get increasingly complicated until landing on the moon is actually the easier proposition.

See also[edit]


  1. The whole sad story is in Voodoo Science, ©2000 by Robert Park.
  2. Hint: ionizing starts in the visible light spectrum somewhere around indigo. Radio waves aren't, even when they get up into the hundred-gigahertz range.