Quote 88
I have no understanding of it and I am not sure that I believe in it. Perhaps it was a sin to kill the fish. I suppose it was even though I did it to keep me alive and feed many people. But then everything is a sin. Do not think about sin. It is much too late for that and there are people who are paid to do it. Let them think about it. You were born to be a fisherman as the fish was born to be a fish. San Pedro was a fisherman as was the father of the great DiMaggio. (4.103)
The old man uses the notion of a natural order to placate his thoughts of sin.
Quote 89
Besides, he thought, everything kills everything else in some way. Fishing kills me exactly as it keeps me alive. The boy keeps me alive, he thought. I must not deceive myself too much. (4.108)
The old man recognizes that companionship is necessary in the natural order of the world.
Quote 90
The old man made the sheet fast and jammed the tiller. Then he took up the oar with the knife lashed to it. He lifted it as lightly as he could because his hands rebelled at the pain. Then he opened and closed them on it lightly to loosen them. He closed them firmly so they would take the pain now and would not flinch and watched the sharks come. He could see their wide, flattened, shovel-pointed heads now and their white tipped wide pectoral fins. They were hateful sharks, bad smelling, scavengers as well as killers, and when they were hungry they would bite at an oar or the rudder of a boat. It was these sharks that would cut the turtles’ legs and flippers off when the turtles were asleep on the surface, and they would hit a man in the water, if they were hungry, even if the man had no smell of fish blood nor of fish slime on him. (4.114)
Despite excusing his own behavior based on Darwinistic reasoning, the old man still passes a seemingly moral judgment on the sharks that attack his boat.