# the blind

Yahweh speaks of his people being helpless as if they could not see because they were blind. 

# that they do not know

Possible meanings are 1) "that they have never traveled" or 2) "with which they are unfamiliar."

# I will turn the darkness into light before them

Yahweh speaks of his people being helpless as if they could not see because they walked in darkness, and of his helping them as if he caused light to shine in the darkness.