Metaphor-
Eg: a) ‘the head is held high’ (physically speaking, Indians could hold their heads high, but this expression is used to show how Indians were considered lower humans than the British. Only the rulers could live dignified lives.)
b) ‘Where the world has not been broken up into fragments
By narrow domestic walls’ (The walls being talked about are not physical structures of brick and cement, but the walls of narrow-minded thinking, like caste system)
c ) ‘the clear stream of reason’ (The poet compares a logical mind to a clear stream. In both cases, clear water is good and muddy water is not desired.)