In his starting section, "Path", Macfarlane admits that not all walkers are benign or appealing. While I think he is a little hard on Morris Dancers and people who walk in sandals (p. 23) he does mention that trampers can have more sinister motives than mere enjoyment of nature and movement. He mentions people who walk because they are delusional or racist.
He also discusses two writers who walked to stave off depression - 19th-century walker George Borrow and poet Edward Thomas, who was killed in World War I. Borrow, who rode around on a black Arab stallion when at home, walked over not only England but also France, Spain, Portugal, Russia, and Morocco. He knew twelve languages and was acquainted with another forty. The activity of walking exposed him to new people and allowed him to exercise his mind as he exercised his body.
Edward Thomas and his poetry had the most influence over Macfarlane. The author admits that Thomas is the guiding spirit of his book (p. 24) and his first walk in The Old Ways is one that Thomas took a hundred years earlier. Macfarlane says that while Thomas
"was drawn to the romantic figure of the self-confident solitary walker, he was more interestingly alert to how we are scattered, as well as affirmed, by the places through which we move" (p. 25).
Thomas appears throughout The Old Ways, and Macfarlane gradually tells the story of Thomas's life in the "Ghost" section of the book. Thomas suffered badly from depression and moved frequently in the hopes that his new house would help him battle it; walking was a similar way to stave it off.
Interestingly enough, American poet Robert Frost knew Thomas. The famous Frost poem, "The Road Not Taken", was inspired by a walk that Frost and Thomas took together. When Frost sent Thomas a draft of the poem, Thomas decided that it was a sign that he should enlist in the British army. He was later killed in France in 1917.