It is chiefly imagistic and involves symbolism, often private in nature; you can think of Eliot and Yeats
it is subject because teacher is a subject
The Greek poets believed the earth to be flat and circular, their own country occupying the middle of it, the central point being either Mount Olympus, the abode of the gods, or Delphi, so famous for its oracle.
Based on this passage, a reader could infer that the ancient Greek poets: were conceited
Brutus, he killed Caesar because of Caesar's ambition.
Hope this helps. - M