Roger Bacon

English friar and philosopher — who argued for empirical observation and experimentation in natural philosophy centuries before Francis Bacon — made contributions to optics, calendar reform, and the theory of lenses — sometimes called the first scientist.

Creates the medieval case for empirical natural philosophy — Bacon's argument (that true knowledge of nature requires observation and experiment rather than pure deduction from authority) anticipates the Scientific Revolution's method by 300 years and makes him the most important medieval advocate of what became science.