Any testable theory proposed to explain a set of observable facts.
All knowledge depends on hypotheses that account for the regular behavior of phenomena.
A working hypothesis is confirmed by testing its ability to predict the behavior of phenomena other than the facts on which it is based. Such propositions are accepted as true because they have yet to be falsified by direct observation. Hypotheses are established as valid when they are able to account for the bulk of the evidence. It is validated or falsified by comparing all the details of the complete works, not just a few passages. Sometimes observed facts may not confirm a hypothesis and still not threaten its validity.