The phrase "chief purpose" refers to an individual's or a group's primary objective, goal, or reason for existence. It is the fundamental reason why someone does something and it serves as the guiding principle in their actions and decisions.
More of it comes from wealthy individuals and corporations whose chief purpose is to have access to, and influence on, government officials. (religion-online.org)
The second chief purpose of classifying is to facilitate control of things. (religion-online.org)
He also rejected as inhuman King's command to love the enemy: «It is not possible to love a man whose chief purpose in life is to humiliate you and still be considered a normal human being.» (religion-online.org)