In naturalism, nothing is at random and everything is explainable. Every event can be explained in terms of natural causes, or natural laws. Pèpe's death was justified by nature. It was as if he was a polar bear with no fur, which clearly can't survive in its natural habitat. Pèpe didn't have any sense of nature's obstacles. As the less intelligent being of nature, he was destined to die at a level below those that could survive. Naturalism doesn't attribute spiritual or supernatural support of any kind. Pèpe couldn't be saved by any means of a miracle. The story had followed the philosophy of naturalism throughout Pèpe's entire journey. His fate could be evidenced by the stupid actions he took to try and save himself, such as putting the dirty spider web in his cut, resulting in an infection. The philosophy of naturalism is a way of having everything be explained by nature.
Flight supports naturalism by giving detailed explanations to Pèpe's actions and consequences. The environment that Pèpe was in didn't seem to offer any help to him due to the demanding climate "The dust gathered quickly in the deep valley."(Steinbeck, Flight, 434) He wandered into the valley hoping for help, but only came into more trouble. Nature wasn't intending to help him survive. He was unprepared and therefore didn't have a chance to last amongst the others. We see Pèpe's environment ripping him apart, indeed, as he walks "The brush grabbed at his legs in the dark until one knee of his jeans was ripped."(Steinbeck, Flight, 434) Pèpe didn't have knowledge