What are the motifs in The Dharma Bums by Jack Kerouac?

Nature is a recurring idea.

The characters in the novel spend a huge amount of time out-of-doors experiencing nature. For some, like Japhy Ryder and Henry Morley, this experience is a common one. For other characters, like Ray Smith, the connection with nature is new, exhilarating and energizing. Even though Ray has clearly spent many days traveling out-of-doors, he has not previously conceptually connected with nature in the way he does throughout the novel.