Cardinal Bellarmine gave a well known example of the older sense of the word in the warning issued to Galileo in the early 17th century : that he must not treat the motion of the Earth as a reality , but merely as a hypothesis . Cardinal Bellarmine gave a famous example of this usage in the warning issued to Galileo in the early 17th century : that he must not treat the motion of the Earth as a reality , but merely as a hypothesis .