Why would Milton begin "Aeropagitica" with a verse from the Suppliant Women?

It is the content of the quote rather than its source that motivated Milton to use it at the beginning of "Aeropagitica." In many ways, the excerpt reflects a central theme of the essay, which was written to argue against the licensing of books by the Crown, a practice that allowed the government to censure written material. The excerpt is saying essentially that liberty and justice depend in no small part on the ability to "speak free," and make one's views heard. Milton makes the same point in "Aeropagitica." Licensing and censorship, he argued, should anger every "learned and religious men," because they both restricted the expression of ideas and gave bad ideas more publicity than they should receive. Comparing truth to a "streaming fountain," Milton claimed that without the "perpetuall" flow of new ideas, might become a "muddy pool of conformity." So Milton argues, like the passage from the Suppliants suggests, that men should be allowed the freedom to express their ideas.