Observation. Also referred to as the Scientific Method. At the heart of science lies the scientific experiment. The method of science is rather straightfoward. By some means, usually be reasoning deductively from existing theory or inductively from existing facts or through intuition, the scientist arrives at a hypothesis about some feature of reality. He then designs an experiment to objectively test the hypothesis. The data from the experiment are then analyzed statistically, and the hypothesis is either supported or rejected.
The feature of overriding importance in this methodology is that no matter what the scientist believes is true regarding the hypothesis under study, the experiment provides the basis for an objective evaluation of the hypothesis. The data from the experiment force a conclusion which is consonant with reality. Thus, science has a built-in safeguard for assuring that truth assertions of any sort about reality must conform to what is demonstrated to be objectively true about the phenomena before the assertions are given the status of scientific truth.
An important aspect of this method is that the experimenter can be wrong in his hunches and the data will tell him so. He can then alter his hypothesis in light of the data and test the new hypothesis. This method, however, can be painstakingly slow, but has a self-correcting feature which, over the long run, has a high probability of yielding truth.