How do his observations about nature help develop his central idea about solitude

Thoreau seeks first to explain why he is not lonely while living "alone" in the woods, Instead of simply filling time with meaningless conversation and company, Thoreau argues that we ought to abandon this pretense and only engage with others for "all important and hearty communications." Quality, not quantity, is the sought after trait. Solitude in when immersed in nature becomes a cathartic experience. He takes care to emphasize that all parts of nature -- the lake, bumble bees, the North Star -- are companionship for him and that he is not lonesome.