How is the idea of human nature explored by in "The Sniper" by Liam O’Flaherty?

O'Flaherty does not suggest that humans are inherently good nor inherently bad. Therefore, he makes no overarching statement about which way human nature tends to lean. He may have an opinion on this but he does not make it clear in this story. He does show how humans are capable of becoming used to killing, notably in the situation of war. When the sniper kills the solider, the old woman, and the enemy sniper, he...

O'Flaherty does not suggest that humans are inherently good nor inherently bad. Therefore, he makes no overarching statement about which way human nature tends to lean. He may have an opinion on this but he does not make it clear in this story. He does show how humans are capable of becoming used to killing, notably in the situation of war. When the sniper kills the solider, the old woman, and the enemy sniper, he is killing the enemy. He is able to ignore the thought that he is killing people, let alone fellow citizens, or even a brother. In the opening paragraphs, the author describes the sniper: 

His face was the face of a student, thin and ascetic, but his eyes had the cold gleam of the fanatic. They were deep and thoughtful, the eyes of a man who is used to looking at death. 

This passage is telling because it demonstrates a notion of human nature. The sniper had the face of a student. This indicates youth, naivety, and maybe even innocence. But after experiencing war, he has become cold, fanatical, and "used to looking at death." He is able to become robotic in this way. But that initial innocence, that potential for compassion never really goes away. It is suppressed until he looks into the face of his brother. Then the compassion returns. This suggests that human nature is here presented as having the potential for compassion and indifference. In this analysis, O'Flaherty shows how our human nature is malleable, capable of good and evil.