Empiricism is a theory that states that knowledge comes only or primarily from sensory experience. It is one of several views of epistemology, the study of human knowledge, along with rationalism and skepticism. Empiricism emphasizes the role of empirical evidence in the formation of ideas, over the notion of innate ideas or traditions; empiricists may argue however that traditions (or customs) arise due to relations of previous sense experiences.
Empiricism in the philosophy of science emphasizes 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.
Empiricism, often used by natural scientists, says that "knowledge is based on experience" and that "knowledge is tentative and probabilistic, subject to continued revision and falsification." One of the epistemological tenets is that sensory experience creates knowledge. Empirical research, including experiments and validated measurement tools, guides the scientific method.
The English term empirical derives from the Ancient Greek word ἐμπειρία, empeiria, which is cognate with and translates to the Latin experientia, from which are derived the word experience and the related experiment. The term was used by the Empiric school of ancient Greek medical practitioners, who rejected the three doctrines of the Dogmatic school, preferring to rely on the observation of "phenomena".