The last paragraph of her address is probably the most poetic part of the whole speech. At first it seems like a bit of a non sequitur, but then you realize that she's making a lyrical conclusion statement that brings it all together:

Our roots are in the dark; the earth is our country. Why did we look up for blessing – instead of around, and down? What hope we have lies there. Not in the sky full of orbiting spy-eyes and weaponry, but in the earth we have looked down upon. Not from above, but from below. Not in the light that blinds, but in the dark that nourishes, where human beings grow human souls. (69-74)

One of the important things to remember is that she was speaking this speech…you know, like, out loud. Because if you just read it quickly, it can get a bit confusing. (Our only hope lies in the earth we look down upon, from below? Huh?) So if you inject the appropriate pauses for emphasis, it makes way more sense:

Our roots are in the dark; the earth is our country. / Why did we look up for blessing – instead of around, and down? What hope we have lies there. / Not in the sky full of orbiting spy-eyes and weaponry, but in the earth we have looked down upon. / Not from above, but from below. / Not in the light that blinds, but in the dark that nourishes, where human beings grow human souls. (69-74)

Can you see the difference?

And then we get to her very last sentence. She claims that our only hope lies "Not in the light that blinds, but in the dark that nourishes, where human beings grow human souls." That's one of those statements that you could contemplate for days. Why is the dark nourishing? Can human beings grow human souls in the light? Is soul-growing like reverse photosynthesis?

But that's Le Guin in a nutshell: always thought-provoking.