9. Plato believed that population control was a duty of the state
In his Republic, Plato expressed his belief that population growth was a leading cause of war, since increased population demanded increased territory for its support. He proposed the idea of a ruling class, which he called the Guardians. The Guardians were to hold both property and mates in common, sharing both among themselves. The Guardians were to impose legal restrictions on reproduction within the state, thus achieving and maintaining the balance necessary to ensure harmony. It was Plato’s belief that strife between the classes of society and wars of conquest would be eliminated, and all states would achieve their natural state of balance.
Plato called the state of balance the “realm of temperance”, which could only be achieved through the action of the ruling class. He supported the idea of easing pressure caused by overpopulation by creating colonies, with forced emigration of people to them. Plato also advocated the state limiting the number of households allowed within its boundaries. He called overpopulation a circumstance of “desperation”, due to a “superabundance of citizens, owing to the mutual affection of those married” and recommended colonization – essentially exile – to new states modeled along the lines he suggested in the Republic and subsequent works.