Companionship
Companionship is one of the most important themes in A Dog of Flanders. Nello was born without any siblings and often had no friends. He had no companions in his life—until he meets Patrasche. Afterwards, he spends every waking moment with his trusty dog, who he becomes friends with and who act as each other companions. In fact, they spend every waking moment together, including their last moments alive after they die of hypothermia in the cathedral. Companionship, the novel argues, is one of the most important things that a person can have. Without it, their life would not be as interesting and fulfilling and meaningful. Companionship is what makes humans, human.
Family
Family is another important theme in the novel. At a very young age, Nello's mother died in a tragic manner. His father had previously left he and his mother, leaving Nello's grandfather as the only person who was willing to take Nello in. That means that Nello's grandfather is the only family that he has in life. For Nello, this underscores the importance of family and having family in your life. That's why, when his landlord threatens to evict Nello and his grandfather, Nello steps up to the plate and starts selling milk to support himself and his grandfather.
Overcoming adversity
Overcoming adversity is one of the most important themes in the novel. In the novel, Nello and Patrasche must overcome adversity in a number of ways. For instance, at the start of the novel, Nello must overcome the adversity of losing his mother at such a young age. Then, he must overcome the adversities of not having enough money to survive (on multiple occasions) and the adversity of not having the approval of his love interest's father. Then, his final adversity is the loss of his home, which forces him to become homeless and which ultimately leads to his death. Despite overcoming so much so early in his life, the boy cannot overcome one of the important adversities in his life: the lack of a warm place to sleep in at night.
