The following text is a very important quotation from the book:

The Lighthouse was then a silvery, misty-looking tower with a yellow eye, that opened suddenly, and softly in the evening. Now—James looked at the Lighthouse. He could see the white-washed rocks; the tower, stark and straight; he could see that it was barred with black and white; he could see windows in it; he could even see washing spread on the rocks to dry. So that was the Lighthouse, was it?
No, the other was also the Lighthouse. For nothing was simply one thing. The other Lighthouse was true too.

Write an essay (25-30 lines) having as starting point the quotation above.

Good luck!