This short story intimately concerns the psychology of children, and in particular, how the way a child sees the world conflicts so often with how an adult sees it. We are presented with a scene with two children who are both busily involved in their own activity, the girl reading, the boy playing, and then the boy's Nurse enters and tells the boy off because he is not playing with the girl. The boy goes into a tantrum, and the girl and Nurse leave. Moments later, however, the girl re-enters, only for both of them to resume the exact activities they were engaged in before, and the same tranquility and peace descends on the scene.
Note how Tom responds to his Nurse when he is told off for ignoring Jenny and not playing with her:
"She's not by herself," Tom said.
"Oh, Tom, that really is naughty of you. Where are all your nice manners? Get up, my dear, and play with her like a good boy."
"I am playing with her," Tom said, in a surly tone, and he gave Nurse a sidelong glance of anger.
Here we have the conflict presented in stark terms. The "nice manners" of the adult world are opposed by the child's instinctive understanding of what it means to "play" with someone and being with someone. Tom and Jenny, even though they are both engaged in different activities, are perfectly happy and playing "together" even though they are not doing the same thing. It is the imposition of the adult's view that makes Tom suffer a "large and complicated grievance." Perhaps, the story suggests, we as adults have a lot to learn from the way that children see the world.