Posted by Brian Sandine on November 22, 2002
After further research, it appears that this quotation can be traced to Plato's Republic, book II, 369C, which was written 360 B.C.
When Socrates and Adeimantus discuss the origin of the State (and the nature of justice and injustice as they appear in the ideal State), Socrates makes two statements:
" A State, I said, arises, as I conceive, out of the needs of mankind". . ."let us begin and create in idea a State; and yet the true creator is necessity, who is the mother of our invention."