Roger Bacon
English Franciscan monk and scientist (1214?-1294?) who is credited with formalizing the modern scientific method. Bacon's influence on modern rationalism is hard to overstate; although his interests in alchemy and astrology are now thought of as medieval superstition, they were the received knowledge of his time to which he added a new focus on empirical evidence. In particular, he described the refraction of light, and developed the earliest recorded formula for gunpowder (an Asian invention which Europeans had most likely heard of but not reproduced).
After attempting to summarize all scientific knowledge on a commission for Pope Clement IV, Bacon fell out of favor with the Church and spent years in prison, accused of heresy. Much of his writing was lost, while myths about him persisted, such as his mechanical head.
James Blish's biographical novel Doctor Mirabilis (1964) is not only a fascinating evocation of Bacon's mind, medieval scholarship and Church politics, but also connects to Riddley Walker at another point: the dream scene in which Bacon receives the secret of gunpowder from a "still unbroken" man "at the heart of an explosion" seems to be an early appearance of the Addom.