The central theme in “Lather and Nothing Else” is that when faced with hard decisions people struggle with their morals. In this story the protagonist is faced with the decision to become a murderer or continue being the honorable barber that he is.
The first reference to support this theme is when the barber thinks to himself “I would have to shave his beard just like any other, carefully, neatly, just as though he were a good customer...” Showing that his first instinct is to let the Captain live and to give him the best shave he possibly can.
But as the time goes on, and the more the captain talks about the killing of the revolutionaries the barber starts having other thoughts “... And it would be so easy to kill him. He deserves it. Or does he? ... I could cut his throat...” Which show that the internal battle to go against his morals is becoming more intense.
Another example of the internal struggle the barber is having is when he thinks “I could cut his throat...” showing that he is considering killing the captain. Then in his next thought he is putting doubt in his mind about it:
And what would I do with the body? Where would I hide it? I would have to flee, leave all this behind, take shelter far away, very far away. They would follow until they caught up with me.
In the end the barber is true to himself and lets the captain live:
But I don’t want to be a murderer. No, sir. You came in to be shaved. And I do my work honorably don’t want to stain my hands with blood. Just lather and nothing else.