Moral theory develops from the divine command theory of medieval Christian philosophy, mixed up with a bit of ancient pagan virtue theory, to the purely secular moral sentiment and interpersonal reaction theories of Smith and Hume, to Kant's attempt to restore command theory but with something supersensible in the individual rather than God as the source of authority.
In small settlements everyone knows your affairs. In the city everyone does not-only those you choose to tell will know about you. This is one of the attributes of cities that is precious to most city people.