empiricism

Short definition from Wiktionary

Noun

1. 1
   A doctrine which holds that the only or, at least, the most reliable source of human knowledge is experience, especially perception by means of the physical senses. (Often contrasted with rationalism.)
2. 2
   A pursuit of knowledge purely through experience, especially by means of observation and sometimes by experimentation.
3. 3
   Research methodology shaped from empirical philosophy (see above), e.g. surveys, statistics, etc.
4. 4
   Medicine as practised by an empiric, founded on mere (personal or anecdotal) experience, without the aid of science or a knowledge of principles.