Empiricism is a theory of knowledge that asserts that knowledge arises from sense experience. Empiricism is one of several competing views that predominate in the study of human knowledge, known as epistemology. Empiricism emphasizes the role of experience and evidence, especially sensory perception, in the formation of ideas, while discounting the notion of innate ideas (except in so far as these might be inferred from empirical reasoning, as in the case of genetic predisposition).
In a related sense, empiricism in the philosophy of science emphasizes those aspects of scientific knowledge that are closely related to evidence, especially as discovered in experiments. It is a fundamental part of the scientific method that all hypotheses and theories must be tested against observations of the natural world, rather than resting solely on a priori reasoning, intuition, or revelation. Hence, science is considered to be methodologically empirical in nature.
The term "empiricism" has a dual etymology. It comes from the Greek word ἐμπειρία, which translates to the Latin experientia, from which we derive the word experience. It also derives from a more specific classical Greek and Roman usage of empiric, referring to a physician whose skill derives from practical experience as opposed to instruction in theory.