Thoreau writes in his journal:
How important is a constant intercourse with nature and the contemplation of natural phenomena to the preservation of moral and intellectual health! The discipline of the schools or of business can never impart such serenity to the mind. The philosopher contemplates human affairs as calmly and from as great a remoteness as he does natural phenomena. The ethical philosopher needs the discipline of the natural philosopher. He approaches the study of mankind with great advantages who is accustomed to the study of nature.
