In
science, a theory is a
mathematical or
logical explanation, or a testable
model of the manner of interaction of a set of
natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through
experiment or otherwise
falsified through
empirical observation.
It follows from this that for
scientists "theory" and "fact" do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behavior are Newton's theory of
universal gravitation (see also
gravitation), and the theory of
general relativity.
In common usage, the word
theory is often used to signify a
conjecture, an
opinion, or a
speculation. In this usage, a theory is not necessarily based on
facts; in other words, it is not required to be consistent with
true descriptions of
reality. This usage of theory leads to the common incorrect statements. True descriptions of reality are more reflectively
understood as statements which would be true independently of what people think about them.