Again regarding the theory that the Earth moves (a highly controversial hypothesis at the time), he cites Galileo, who praises the "followers of the Pythagorean opinion [that the earth moves]." He specifically refers to those who choose to trust their logic and rationality over the countless observations via senses that oppose the theory of the movement of Earth.
Another observational example, other than the tower argument (mentioned yesterday), that strongly shows otherwise deals with the movement of other planets and is described by Galileo:
Mars, when it is close to us...would ahve to look sixty times as large as when it is most distant. Yet no such difference is to be seen. Rather, when it is in opposition to the sun and close to us it shows itself only four or five times as large as when, at conjunction, it becomes hidden behind the rays of the sun.Furthermore, regarding Copernicus and his revolutionary (no pun intended) ideas for Venus, Galileo states:
I cannot get over my amazement that he was constantly willing to persist in saying that Venus might go around the sun and might be more than six times as far from us at one time as at another, and still look always equal, when it should have appeared forty times large.
Feyerabend cites these observational arguments to show that such claims only create an illusion that prevents us from discovering the truth, and that rationality must be prioritized in order to escape such illusions.
Yet overcoming one's senses and replacing them with reasoning is no small feat. This explains why Galileo so admires those who "have, through sheer force of intellect, done such violence to their own senses as to prefer what reason told them over that which sensible experience plainly showed them to be the contrary."
*All quotes by Galileo were from his Dialogue Concerning the Two Chief World Systems, and were taken from Feyerabend's essay.