Bello and Whitman both value first-handedness, but Bello is much more exclusive about it. Bello views modernization and cities with utter contempt, and weeps at their creation. Thoreau tends toward the side of Bello in that he sees the modern world as inferior to the natural. Whitman accepts all things as life, and thinks that all life has value. One thing they all have in common, however, is their value in personal experience. They all can agree that experiencing nature is a spiritual experience, and it is to be revered. They all write about how much they enjoy nature and how their connection to it is triggered by physical view and/or contact.
Whitman sees modernization as a natural process, and is accepting of it. He embraces every form of life, and all of nature is included in that description.