The speaker is a lonely poet who has learned how to keep himself company by viewing nature as "peopled" by things. The first two lines make him sound almost like the cliché of a Romantic poet: his sensitive and intelligent nature puts him so far above everyone and everything else that he can’t help but feel a noble loneliness. He lives in a rural area and likes to take long walks by himself, which isn’t exactly the best cure for loneliness. Fortunately, the speaker doesn’t stay in this funk for long. He has a vibrant imagination, and can create the effect of having people around him without actually having people around him.
We know that the speaker is a poet because he tells us so in line 15. He speaks in the third person, but we know he’s talking about himself. Also, we have the sense that this poet takes nature to be almost a religion, and he brings intense focus and attention with his "gaze" on nature. He also has an "inward," spiritual eye that seems more powerful (or at least equally powerful) than his regular vision.