The adjective empirical derives from the Greek ἐμπειρία (empeiria, ‘experience’) and means ‘relating to or derived from experience rather than theory’. The word has distinctive uses in philosophy and in medicine.
In philosophy and related disciplines a statement is said to be an empirical statement if its truth or falsity is to be established by observation, experiment, sociological survey, the collection of evidence, and the like – for example, ‘The sun is shining at the moment’, ‘Oak trees shed their leaves in autumn’, ‘Queen Victoria died in 1901’, and ‘Water boils at 100°C’. Empirical statements may be contrasted with statements whose truth or falsity is established not by observation or experiment but in some other way – for example, statements such as ’All bachelors are unmarried’ and ‘Some bachelors are women’, the truth or falsity of which is evident from the meaning of the words used to express them; and geometrical theorems (such as Pythagoras’ theorem, that the square on the hypotenuse of a right-angled triangle is equal to the sum of the squares on the other two sides), the truth of which is established not by observation but by deduction from axioms or first principles.
In medicine a course of treatment is said to be empirical when it is based on practical experience rather than scientific proof – e.g., a drug is prescribed empirically (for a certain condition) when the prescription is justified by the drug’s having regularly in the past proved effective (against this condition), even though the medical profession cannot explain its effectiveness.
Empiricism is the philosophical position that all knowledge is based on experience derived from the senses. Empiricism may be contrasted with rationalism, the position that some knowledge is based on the use of reason independently of the senses. Empiricist theories were famously developed by John Locke (1632-1704), in his Essay Concerning Human Understanding, George Berkeley (1685-1753) in his Principles of Human Knowledge, and David Hume (1711-1776) in his Treatise of Human Nature. These three philosophers are sometimes referred to collectively as ‘the British Empiricists’.