We must now consider the vices opposed to knowledge and understanding.
Since, however, we have treated of ignorance which is opposed to knowledge, when we were discussing the causes of sins ( FS, Q ), we must now inquire about blindness of mind and dulness of sense, which are opposed to the gift of understanding; and under this head there are three points of inquiry:
A Whether blindness of mind is a sin?
A Whether dulness of sense is a sin distinct from blindness of mind?
A Whether these vices arise from sins of the flesh?