The Trials of Becoming a Man
Throughout A Day No Pigs Would Die, Robert is presented with trials that test and toughen his character, gradually bringing about his transition into manhood. When Robert is forced to allow his best friend to be butchered so that the family can eat, it shows that he has accepted that some things in life are inevitable and that being a man is all about doing what has to be done.
The Difficulty of Being an Outsider
Robert Peck is not like the other boys that he goes to school with in Learning, Vermont. He is the son of an impoverished farmer and a Shaker, both of which create a sense of isolation in Robert. He does not deal well with being different in the beginning of the book, as shown when he runs away from his trouble at school and does everything he can to avoid going back. Later in the book when Robert becomes a man, he accepts his position in life and discovers that Pinky has not been his only friend.
Free Will versus Expectations
All of the major characters in A Day No Pigs Would Die are people who, though easily seen within certain categories (e.g. farmer, Shaker, adolescent), assert their individuality by displaying original ideas and attitudes toward life. Haven, for example, is a devout Shaker, but when his son asks him if he believes in all of the Shaker Laws, he only replies, "Most." In several situations he goes against Shaker ways to make his own decisions. Mrs. Peck exhibits this same characteristic. When Aunt Carrie is fretting over the adultery of the Widow Bascom, Mrs. Peck gives her approval for the way the widow carries on with life after her husband dies.
Acceptance of the Inevitabilities
A Day No Pigs Would Die is all about the way that its characters react to the traumatic events that they experience. One of the things that Haven tries to teach his son is that there is nothing that they can do about these tragedies except carry on. When Haven dies in the end of the book, his son and family show that they have learned this lesson thoroughly by carrying on with life as if it were any other day.