'I can only meditate when I am walking,' wrote Jean-Jacques Rousseau in the fourth book of his Confessions, ‘when I stop I cease to think; my mind only works with my legs.’ Soren Kierkegaard speculated that the mind might function optimally at the pedestrian pace of three miles per hour, and in a journal entry describes going out for a wander and finding himself ‘so overwhelmed with ideas’ that he ‘could scarcely walk’. Christopher Morley wrote of Wordsworth as ‘employ[ing] his legs as an instrument of philosophy’ and Wordsworth of his own ‘feeling intellect’. Nietzsche was typically absolute on the subject — ‘Only those thoughts which come from walking have any value’ — and Wallace Stevens typically tentative: ‘Perhaps / The Truth depends on a walk around a lake.’

Robert Macfarlane, The Old Ways