Falsifiability is the term coined by Karl Popper for the idea that a hypothesis or theory addresses the observable world only insofar as it can be found false as the result of some observation or physical experiment. For instance, the proposition "All cats have fur" can easily be proven false with the observation of a single hairless cat. The proposition "The world will end in the year 3035" is impractical to falsify, but still passes the test of falsifiability in that there exists the logical possibility that 3035 will come and go without the world ending. To the contrary, it is possible to posit that everything that happens is the will of Zeus. No matter what experiment we design – such as praying to Zeus to give us the answer or daring Zeus to strike us with lightning – we can always infer that the result is the will of Zeus. Such a proposition, as conceived here, is not falsifiable. Popper claimed that a falsifiable theory is the only kind that can truly be scientific, or at least useful to the scientific community. By that logic, we can also say that no theory should be formed that has no chance of being true. However, seeing as that kind of theory is much less likely to be formed, it is understandable that Popper does not devote that much time to the criterion of "confirmability."