known as Doctor Mirabilis (‘marvellous doctor’). A member of the Franciscan order, Bacon began his career studying the previously forbidden works of Aristotle. However, he mixed his admiration for science with a relatively uncritical interest in Neoplatonic, astrological, and occult learning. His principal work is the Opus Maius (‘Greater Work’) detailing the causes that have hindered the progress of philosophy. Shorter works include the Opus Minus (‘Lesser Work’) and Opus Tertius (‘Third Work’). Bacon's writings show remarkable prescience, particularly in his use of mathematics, his investigations into the science of optics, and a stress on correct use of experience and language, but his work is generally regarded as uneven in quality, mingling uncritical respect for authority with real philosophical and scientific insight. However, he is credited with inventing spectacles. In 1277 Bacon's work was condemned by the Franciscan order for ‘suspect novelties’ and Bacon is said to have been imprisoned for a time.