Many empirical sciences have special techniques, methods, or tools to make observations in systematic ways that make it likely the observations can be repeated by other people qualified to make them, thereby giving them an intersubjective and possibly objective status.

And in many empirical sciences, such as physics and chemistry, one of the basic rules that makes these sciences empirical is that experiments that cannot be repeated by others with the same kinds of observable effects have no value as evidence. Conversely, if an experiment generates observations that are new and these can be repeated by independent qualified others, the observations do count as evidence for or against a theory that implies or denies their existence.