Observation: What has been experienced
in some reality by various
persons, especially by some
scientific method, including apparatuses
like microscopes, telescopes etc.
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
can be repeated by independent qualified others, the observations do
count as evidence for or against a theory that implies or denies their
Note that, as defined, the difference between an observation
and an observable is merely that the former
has been made, and the latter is supposed to be possible but has not
(yet) been made.
Note also that it is not necessarily true that observations once made
remain forever (presumptively) true: People may be mistaken, and they
also may lie about what they have observed. The checks introduced by
scientific method serve
to make it as rationally credible as possible that in actual fact the
observations have been made and reported impartially and objectively,
and can be checked and repeated by qualified persons.