What makes the urgency of the child's demand seem logical?
The child is young and impatient. When he hears the mother discussing things with the father, on hearing her voice reminds him that he is hungry. So, he goes up to her asking for food. Even on being gestured by the mother to wait for five minutes he demands food throwing his logic at her that he will not be hungry any more. The argument is appealing to the father, he feels that a boy, so young, who is “such a logician deserves his dinner straight away.” The urgency with which the boy demands and with such wittiness makes the mother laugh. This joy held the three together. The mother then agrees to serve the dinner and they go inside the house.