Changes wrought by printing had a more immediate effect on cerebral activities and on the learned professions than did many other kinds of ‘external’ events. Previous relations between masters and disciples were altered. Students who took full advantage of technical texts which served as silent instructors were less likely to defer to traditional authority and more receptive to innovating trends. Young minds provided with updated editions, especially of mathematical texts began to surpass not only their own elders but the wisdom of ancients as well. Methods of measurement, records of observations and all forms of data collection were affected by printing. So too were the careers that could be pursued by teachers and preachers, physicians and surgeons, reckon-masters and artist-engineers. “It is easy to agree with . . . contentions that a neat separation of internal and external factors is out of the question . . . but, as G. R. Elton wrote several years ago, there is work to be done rather than called for.”