The theme of William Wordsworth's poem "The World Is Too Much With Us" is one of vision. What is meant by this is the theme refers to how one regards the world around them when their vision is obscured.
The first time the theme is seen is in the third line: "Little we see in Nature that is ours." Here, the theme is initially defined. When "we," society, look around, we fail to recognize anything in nature that we can claim. While Wordsworth does not see this as a problem, per say, he does recognize the fact that "we" are competing with things around us.
Later in lines twelve and thirteen, Wordsworth again brings up sight:
Have glimpses that would make me less forlorn;
Have sight of Proteus rising from the sea.
Here, Wordsworth wishes that he could see Protus (a sea-god) rising from the sea. This "sight" has a double meaning. First, the literal: Wordsworth wishes to see the god rising from the sea. Second, and a more figurative interpretation, Wordsworth wishes to be able to see Nature as Proteus does.
In the end, Wordsworth is illuminating the importance of vision, or sight. To exist in the world properly, one must be able to really see things for what they are. Wordsworth does not want "us" to only look.