Falsifiable

A proposal or theory is falsifiable if it can be shown to be false when it is false. A proposal or theory that cannot never be shown to false even though it is false is not falsifiable.

For example, the suggestion that I would be a very happy if I were ten years younger is not falsifiable, and thus not worth thinking about. We have no way of knowing if it is false.

Karl Popper persuasively argued that a theory that is not falsifiable is not scientific, because there is no possible way to disprove it. This is known as the doctrine of falsification.

Carl Sagan

In his book, "Demon-Haunted World" cosmologist Carl Sagan gives an example of a statement with this sort of premise saying: "There is a dragon in my garage." In order for one to prove or disprove the statement they are allowed to ak questions.

• Q. Can I see the dragon?
• A. No, the dragon is invisible.

• Q. Can I tough the dragon?
• A. No, my dragon is incorporeal.

• Q. Can I hear the dragon?
• A. No, my dragon is silent.

In this way, every question can be answered and therefore no the existence of the dragon is unfalsifiable. Simply put: it must exit.