On what grounds can you justify the division of the novel, Hard Times, into three parts with separate titles?

Hard Times is divided into three parts of equal length – Sowing, Reaping, and Garnering. In Sowing, the main characters sow the seeds of their beliefs. Gradgrind sows the seed of Fact; while Bounderby sows the seed of his lies. In Reaping, the men's beliefs grow and take on lives of their own, which successfully builds plot and creates conflict. In the final section, Garnering, or picking up the pieces after a harvest, Bounderby and Gradgrind must pick up and put together the pieces of their own damaged lives.