The title of this lesson may seem to express conflict.
Sight includes the things which can be detected by the physical senses.
Faith is mental, spiritual, and abstract. Yes, but God has used, and continues to use, physical things to make our faith more substantial. Those who make use of graven images and crucifixes in their buildings and who wear medallions and scapulars claim that such objects are merely reminders of spiritual things. In their case, however, they have come to venerate, and look upon, such things as having mystical, sacramental powers. Thus they have become a pitfall to them.