Hypothesis

A hypothesis (foundation from ancient Greek hupothesis where hupo = under and thesis = ) is a proposed explanation for a phenomenon. A scientific hypothesis must be testable and based on previous observations or extensions of scientific theories.

Usage
In early usage, a hypothesis was usually a clever idea or convenient mathematical approach that simplified cumbersome calculations; it did not necessarily have any real meaning. A famous example of the older sense is the warning which Cardinal Bellarmine issued to Galileo, that he must not treat the motion of the Earth as a reality, but merely as a hypothesis.

In common usage at present, a hypothesis is a provisional idea whose merit is to be evaluated. A hypothesis requires more work by the researcher in order to either confirm or disprove it. In the hypothetico-deductive method, a hypothesis should be falsifiable, meaning that it is possible that it be shown false, usually by observation. Note that, if confirmed, the hypothesis is not necessarily proven, but remains provisional.

The term hypothesis was misused in the Riemann hypothesis, which should be properly called a conjecture. As an example, someone who enters a new country and observes only white sheep, might form the hypothesis that all sheep in that country are white. It can be considered a hypothesis, as it is falsifiable. It can be falsified by observing a single black sheep. Provided that the experimental uncertainties are small (for example that it is a sheep, instead of a goat) and that the experimenter has correctly interpreted the statement of the hypothesis (for example, does the meaning of "sheep" include rams?), the hypothesis is falsified. IT is an If/then statement

Propositions
Propositions follow a causal order ("A causes B")

Empirical generalizations
Empirical generalizations are based on observed regularities, but they don't stipulate what is the cause and effect themselves, only stating that 'A is related to B'.

Quotes

 * "Hypotheses non fingo" : "I feign no hypotheses" -- Isaac Newton


 * "... a hypothesis is a statement whose truth is temporarily assumed, whose meaning is beyond all doubt. ..." -- Albert Einstein