Thoreau seems to see Nature as an infant see its mother; large and encompassing, a nurturing provider, and easy to take for granted. He describes Nature in almost religious terms, as an entity that is separate but still innate. His view is almost entirely non-scientific, with information gathered for the purpose of joy, rather than for critical analysis, which was the vogue at the time.
Thoreau views Nature by way of Man; his writing is a constant comparison of the two. While he sees Nature separately, he defines it in terms of Mankind; how it illuminates the character of Man, how it contrasts from Man, and what those things tell us about both Nature and Man.