Derived from the practices of medieval alchemists, the experimental method is at the heart of Western science. It involves these steps:

1. Through observation and research, an educated guess or hypothesis is made concerning the cause and action of the observation.
2. The hypothesis is tested via more observation and the use of controlled experiments to determine its accurateness. If the hypothesis does not explain all of the observations, it needs to be changed. When the final hypothesis explains all data, the method moves to the next stage.
3. The researcher calls on other experimenters to duplicate his or her work. Experiments to prove or disprove a hypothesis are not considered valid unless everything can be successfully reproduced. If others cannot duplicate the research, the original experimenters may return to the beginning and start over or abandon this completely. However, if the research is replicated and other researchers agree with the hypothesis, that hypothesis may be developed into a theory.
4. Theories should be able to predict other observations and behaviors. If experiments by different people show that the theory is correct, and if the theory accurately predicts the observation and behavior of something based on discovery within the theory, that theory becomes a scientific law—until superseded by another theory that better explains all observations.

Thus, a theory in science does not mean one explanation out of many. Rather, it means the best and most complete explanation of all known data.

Also known as the "scientific method."