The structure of the work reflects this cyclic arrangement. It begins with God and his existence in Question 2. The entire first part of the "Summa" deals with God and his creation, which reaches its zenith in man. The First Part, therefore, ends with the treatise on man. The second part of the "Summa" deals with man's purpose (the meaning of life), which is happiness. The ethics detailed in this part are a summary of the ethics (Aristotelian in nature) that man must follow to reach his intended destiny. Since no man on his own can truly live the perfect ethical life (and therefore reach God), it was necessary that a perfect man bridge the gap between God and man. Thus God became man. The third part of the "Summa", therefore, deals with the life of Christ.