The theme of black beauty is that faith and trust are much better than animal cruelty. Author realised this and wrote a book from the perspective of a horse to convey the message to other readers. This was written during a time when horses were still in common use. To stay fashionable, many owners used the horse bearing rein to look good in front of their friends, as Anna Sewell points out. This book teaches us to be kind to people and animals alike.