"La Cité Antique" establishes the importance of studying ancient beliefs to comprehend the societal structures of Greece and Rome. Fustel de Coulanges introduces his argument by highlighting how the perceptions of these societies are often distorted by contemporary views. He intends to show that ancient institutions were intimately connected to their religious practices and that changes in societal structures reflected transformations in human thoughts and beliefs. The author argues that ancient rituals and laws were not arbitrary but were deeply rooted in the spiritual and moral understanding of humanity, setting the stage for a thorough exploration of these themes as the work progresses. (This is an automatically generated summary.)