It is clear that Naturalism, or the utter indifference of nature to the fate of mankind, acts as the major theme of this excellent novel in which the protagonist, Henry, gradually learns about the true nature of courage and heroism and how, no matter how brave we are, we will all face the same end. Again and again he encounters experiences that show to him that the world continues in a way that is completely unaffected by the manner in which men choose to live and die. Such experiences show Henry the falsity of his ideas about manhood and bravery.
One such incident occurs at the end of Chapter Seven, when Henry comes across a corpse in the woods, whose rotting appearance clearly acts as a reminder of how nature and the universe is indifferent towards human existence. Note the appearance of this corpse:
The corpse was dressed in a uniform that once had been blue but was now faded to a melancholy shade of green. The eyes, staring at the youth, had changed to the dull hue to be see on the side of a dead fish. The mouth was open. Its read had changed to an appalling yellow. Over the grey skin of the face ran little ants. One was trundling up some sort of a bundle along the upper lip.
The natural way in which this man's death quickly becomes part of the cycle of nature as it decays and rots forces Henry to realise that death, in spite of all of his fears and misconceived notions, is nothing more than an essential yet unremarkable part of nature.