The tripartite structure of A Passage to India accomplishes a number of objectives that unify the novel. Each of the three sections functions in at least four ways:
The first division, "Mosque," is set in the spring (cool weather) and focuses primarily on the Muslim characters. The atmosphere is calm with an emphasis on reason. Consider the conversation among Aziz and his friends at the dinner party.
Part II, "Caves," takes place in the heat of summer, and emotions are high. Behavior is irrational as the British make bizarre accusations against Aziz.
In the third section, "Temple," the focus is on rebirth and rejuvenation in the rainy fall season as the Hindus celebrate love and the birth of Krishna. Conflict is mostly resolved.
Forster covers three seasons with different kinds of weather, the three main groups in India at the time, and three kinds of behavior with the structure of his novel. This approach provides a unified balance to his treatment of setting, characters, and ideas.